/*-------------------------------------------------------------------------
 *
 * datetime.c
 *      Support functions for date/time types.
 *
 * Portions Copyright (c) 1996-2017, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 * This source code file contains modifications made by THL A29 Limited ("Tencent Modifications").
 * All Tencent Modifications are Copyright (C) 2023 THL A29 Limited.
 *
 * IDENTIFICATION
 *      src/backend/utils/adt/datetime.c
 *
 *-------------------------------------------------------------------------
 */
#include "postgres.h"

#include <ctype.h>
#include <float.h>
#include <limits.h>
#include <math.h>

#include "access/htup_details.h"
#include "access/xact.h"
#include "catalog/pg_type.h"
#include "funcapi.h"
#include "miscadmin.h"
#include "nodes/nodeFuncs.h"
#include "utils/builtins.h"
#include "utils/date.h"
#include "utils/datetime.h"
#include "utils/memutils.h"
#include "utils/tzparser.h"

#ifdef _PG_ORCL_
#include "utils/guc.h"
#endif

static int DecodeNumber(int flen, char *field, bool haveTextMonth,
             int fmask, int *tmask,
             struct pg_tm *tm, fsec_t *fsec, bool *is2digits);
static int DecodeNumberField(int len, char *str,
                  int fmask, int *tmask,
                  struct pg_tm *tm, fsec_t *fsec, bool *is2digits);
static int DecodeTime(char *str, int fmask, int range,
           int *tmask, struct pg_tm *tm, fsec_t *fsec);
static const datetkn *datebsearch(const char *key, const datetkn *base, int nel);
static int DecodeDate(char *str, int fmask, int *tmask, bool *is2digits,
           struct pg_tm *tm);
static char *AppendSeconds(char *cp, int sec, fsec_t fsec,
              int precision, bool fillzeros);
static void AdjustFractSeconds(double frac, struct pg_tm *tm, fsec_t *fsec,
                   int scale);
static void AdjustFractDays(double frac, struct pg_tm *tm, fsec_t *fsec,
                int scale);
static int DetermineTimeZoneOffsetInternal(struct pg_tm *tm, pg_tz *tzp,
                                pg_time_t *tp);
static bool DetermineTimeZoneAbbrevOffsetInternal(pg_time_t t,
                                      const char *abbr, pg_tz *tzp,
                                      int *offset, int *isdst);
static pg_tz *FetchDynamicTimeZone(TimeZoneAbbrevTable *tbl, const datetkn *tp);


const int    day_tab[2][13] =
{
    {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31, 0},
    {31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31, 0}
};

const char *const months[] = {"Jan", "Feb", "Mar", "Apr", "May", "Jun",
"Jul", "Aug", "Sep", "Oct", "Nov", "Dec", NULL};

const char *const days[] = {"Sunday", "Monday", "Tuesday", "Wednesday",
"Thursday", "Friday", "Saturday", NULL};


/*****************************************************************************
 *     PRIVATE ROUTINES                                                         *
 *****************************************************************************/

/*
 * datetktbl holds date/time keywords.
 *
 * Note that this table must be strictly alphabetically ordered to allow an
 * O(ln(N)) search algorithm to be used.
 *
 * The token field must be NUL-terminated; we truncate entries to TOKMAXLEN
 * characters to fit.
 *
 * The static table contains no TZ, DTZ, or DYNTZ entries; rather those
 * are loaded from configuration files and stored in zoneabbrevtbl, whose
 * abbrevs[] field has the same format as the static datetktbl.
 */
static const datetkn datetktbl[] = {
    /* token, type, value */
    {EARLY, RESERV, DTK_EARLY}, /* "-infinity" reserved for "early time" */
    {DA_D, ADBC, AD},            /* "ad" for years > 0 */
    {"allballs", RESERV, DTK_ZULU}, /* 00:00:00 */
    {"am", AMPM, AM},
    {"apr", MONTH, 4},
    {"april", MONTH, 4},
    {"at", IGNORE_DTF, 0},        /* "at" (throwaway) */
    {"aug", MONTH, 8},
    {"august", MONTH, 8},
    {DB_C, ADBC, BC},            /* "bc" for years <= 0 */
    {DCURRENT, RESERV, DTK_CURRENT},    /* "current" is always now */
    {"d", UNITS, DTK_DAY},        /* "day of month" for ISO input */
    {"dec", MONTH, 12},
    {"december", MONTH, 12},
    {"dow", UNITS, DTK_DOW},    /* day of week */
    {"doy", UNITS, DTK_DOY},    /* day of year */
    {"dst", DTZMOD, SECS_PER_HOUR},
    {EPOCH, RESERV, DTK_EPOCH}, /* "epoch" reserved for system epoch time */
    {"feb", MONTH, 2},
    {"february", MONTH, 2},
    {"fri", DOW, 5},
    {"friday", DOW, 5},
    {"h", UNITS, DTK_HOUR},        /* "hour" */
    {LATE, RESERV, DTK_LATE},    /* "infinity" reserved for "late time" */
    {INVALID, RESERV, DTK_INVALID}, /* "invalid" reserved for bad time */
    {"isodow", UNITS, DTK_ISODOW},    /* ISO day of week, Sunday == 7 */
    {"isoyear", UNITS, DTK_ISOYEAR},    /* year in terms of the ISO week date */
    {"j", UNITS, DTK_JULIAN},
    {"jan", MONTH, 1},
    {"january", MONTH, 1},
    {"jd", UNITS, DTK_JULIAN},
    {"jul", MONTH, 7},
    {"julian", UNITS, DTK_JULIAN},
    {"july", MONTH, 7},
    {"jun", MONTH, 6},
    {"june", MONTH, 6},
    {"m", UNITS, DTK_MONTH},    /* "month" for ISO input */
    {"mar", MONTH, 3},
    {"march", MONTH, 3},
    {"may", MONTH, 5},
    {"mm", UNITS, DTK_MINUTE},    /* "minute" for ISO input */
    {"mon", DOW, 1},
    {"monday", DOW, 1},
    {"nov", MONTH, 11},
    {"november", MONTH, 11},
    {NOW, RESERV, DTK_NOW},        /* current transaction time */
    {"oct", MONTH, 10},
    {"october", MONTH, 10},
    {"on", IGNORE_DTF, 0},        /* "on" (throwaway) */
    {"pm", AMPM, PM},
    {"s", UNITS, DTK_SECOND},    /* "seconds" for ISO input */
    {"sat", DOW, 6},
    {"saturday", DOW, 6},
    {"sep", MONTH, 9},
    {"sept", MONTH, 9},
    {"september", MONTH, 9},
    {"sun", DOW, 0},
    {"sunday", DOW, 0},
    {"t", ISOTIME, DTK_TIME},    /* Filler for ISO time fields */
    {"thu", DOW, 4},
    {"thur", DOW, 4},
    {"thurs", DOW, 4},
    {"thursday", DOW, 4},
    {TODAY, RESERV, DTK_TODAY}, /* midnight */
    {TOMORROW, RESERV, DTK_TOMORROW},    /* tomorrow midnight */
    {"tue", DOW, 2},
    {"tues", DOW, 2},
    {"tuesday", DOW, 2},
    {"undefined", RESERV, DTK_INVALID}, /* pre-v6.1 invalid time */
    {"wed", DOW, 3},
    {"wednesday", DOW, 3},
    {"weds", DOW, 3},
    {"y", UNITS, DTK_YEAR},        /* "year" for ISO input */
    {YESTERDAY, RESERV, DTK_YESTERDAY}    /* yesterday midnight */
};

static int    szdatetktbl = sizeof datetktbl / sizeof datetktbl[0];

/*
 * deltatktbl: same format as datetktbl, but holds keywords used to represent
 * time units (eg, for intervals, and for EXTRACT).
 */
static const datetkn deltatktbl[] = {
    /* token, type, value */
    {"@", IGNORE_DTF, 0},        /* postgres relative prefix */
    {DAGO, AGO, 0},                /* "ago" indicates negative time offset */
    {"c", UNITS, DTK_CENTURY},    /* "century" relative */
    {"cent", UNITS, DTK_CENTURY},    /* "century" relative */
    {"centuries", UNITS, DTK_CENTURY},    /* "centuries" relative */
    {DCENTURY, UNITS, DTK_CENTURY}, /* "century" relative */
    {"d", UNITS, DTK_DAY},        /* "day" relative */
    {DDAY, UNITS, DTK_DAY},        /* "day" relative */
    {"days", UNITS, DTK_DAY},    /* "days" relative */
    {"dec", UNITS, DTK_DECADE}, /* "decade" relative */
    {DDECADE, UNITS, DTK_DECADE},    /* "decade" relative */
    {"decades", UNITS, DTK_DECADE}, /* "decades" relative */
    {"decs", UNITS, DTK_DECADE},    /* "decades" relative */
    {"h", UNITS, DTK_HOUR},        /* "hour" relative */
    {DHOUR, UNITS, DTK_HOUR},    /* "hour" relative */
    {"hours", UNITS, DTK_HOUR}, /* "hours" relative */
    {"hr", UNITS, DTK_HOUR},    /* "hour" relative */
    {"hrs", UNITS, DTK_HOUR},    /* "hours" relative */
    {INVALID, RESERV, DTK_INVALID}, /* reserved for invalid time */
    {"m", UNITS, DTK_MINUTE},    /* "minute" relative */
    {"microsecon", UNITS, DTK_MICROSEC},    /* "microsecond" relative */
    {"mil", UNITS, DTK_MILLENNIUM}, /* "millennium" relative */
    {"millennia", UNITS, DTK_MILLENNIUM},    /* "millennia" relative */
    {DMILLENNIUM, UNITS, DTK_MILLENNIUM},    /* "millennium" relative */
    {"millisecon", UNITS, DTK_MILLISEC},    /* relative */
    {"mils", UNITS, DTK_MILLENNIUM},    /* "millennia" relative */
    {"min", UNITS, DTK_MINUTE}, /* "minute" relative */
    {"mins", UNITS, DTK_MINUTE},    /* "minutes" relative */
    {DMINUTE, UNITS, DTK_MINUTE},    /* "minute" relative */
    {"minutes", UNITS, DTK_MINUTE}, /* "minutes" relative */
    {"mon", UNITS, DTK_MONTH},    /* "months" relative */
    {"mons", UNITS, DTK_MONTH}, /* "months" relative */
    {DMONTH, UNITS, DTK_MONTH}, /* "month" relative */
    {"months", UNITS, DTK_MONTH},
    {"ms", UNITS, DTK_MILLISEC},
    {"msec", UNITS, DTK_MILLISEC},
    {DMILLISEC, UNITS, DTK_MILLISEC},
    {"mseconds", UNITS, DTK_MILLISEC},
    {"msecs", UNITS, DTK_MILLISEC},
    {"qtr", UNITS, DTK_QUARTER},    /* "quarter" relative */
    {DQUARTER, UNITS, DTK_QUARTER}, /* "quarter" relative */
    {"s", UNITS, DTK_SECOND},
    {"sec", UNITS, DTK_SECOND},
    {DSECOND, UNITS, DTK_SECOND},
    {"seconds", UNITS, DTK_SECOND},
    {"secs", UNITS, DTK_SECOND},
    {DTIMEZONE, UNITS, DTK_TZ}, /* "timezone" time offset */
    {"timezone_h", UNITS, DTK_TZ_HOUR}, /* timezone hour units */
    {"timezone_m", UNITS, DTK_TZ_MINUTE},    /* timezone minutes units */
    {"undefined", RESERV, DTK_INVALID}, /* pre-v6.1 invalid time */
    {"us", UNITS, DTK_MICROSEC},    /* "microsecond" relative */
    {"usec", UNITS, DTK_MICROSEC},    /* "microsecond" relative */
    {DMICROSEC, UNITS, DTK_MICROSEC},    /* "microsecond" relative */
    {"useconds", UNITS, DTK_MICROSEC},    /* "microseconds" relative */
    {"usecs", UNITS, DTK_MICROSEC}, /* "microseconds" relative */
    {"w", UNITS, DTK_WEEK},        /* "week" relative */
    {DWEEK, UNITS, DTK_WEEK},    /* "week" relative */
    {"weeks", UNITS, DTK_WEEK}, /* "weeks" relative */
    {"y", UNITS, DTK_YEAR},        /* "year" relative */
    {DYEAR, UNITS, DTK_YEAR},    /* "year" relative */
    {"years", UNITS, DTK_YEAR}, /* "years" relative */
    {"yr", UNITS, DTK_YEAR},    /* "year" relative */
    {"yrs", UNITS, DTK_YEAR}    /* "years" relative */
};

static int    szdeltatktbl = sizeof deltatktbl / sizeof deltatktbl[0];

static TimeZoneAbbrevTable *zoneabbrevtbl = NULL;

/* Caches of recent lookup results in the above tables */

static const datetkn *datecache[MAXDATEFIELDS] = {NULL};

static const datetkn *deltacache[MAXDATEFIELDS] = {NULL};

static const datetkn *abbrevcache[MAXDATEFIELDS] = {NULL};


/*
 * strtoint --- just like strtol, but returns int not long
 */
static int
strtoint(const char *nptr, char **endptr, int base)
{
    long        val;

    val = strtol(nptr, endptr, base);
#ifdef HAVE_LONG_INT_64
    if (val != (long) ((int32) val))
        errno = ERANGE;
#endif
    return (int) val;
}


/*
 * Calendar time to Julian date conversions.
 * Julian date is commonly used in astronomical applications,
 *    since it is numerically accurate and computationally simple.
 * The algorithms here will accurately convert between Julian day
 *    and calendar date for all non-negative Julian days
 *    (i.e. from Nov 24, -4713 on).
 *
 * Rewritten to eliminate overflow problems. This now allows the
 * routines to work correctly for all Julian day counts from
 * 0 to 2147483647    (Nov 24, -4713 to Jun 3, 5874898) assuming
 * a 32-bit integer. Longer types should also work to the limits
 * of their precision.
 *
 * Actually, date2j() will work sanely, in the sense of producing
 * valid negative Julian dates, significantly before Nov 24, -4713.
 * We rely on it to do so back to Nov 1, -4713; see IS_VALID_JULIAN()
 * and associated commentary in timestamp.h.
 */

int
date2j(int y, int m, int d)
{
    int            julian;
    int            century;

    if (m > 2)
    {
        m += 1;
        y += 4800;
    }
    else
    {
        m += 13;
        y += 4799;
    }

    century = y / 100;
    julian = y * 365 - 32167;
    julian += y / 4 - century + century / 4;
    julian += 7834 * m / 256 + d;

    return julian;
}                                /* date2j() */

void
j2date(int jd, int *year, int *month, int *day)
{
    unsigned int julian;
    unsigned int quad;
    unsigned int extra;
    int            y;

    julian = jd;
    julian += 32044;
    quad = julian / 146097;
    extra = (julian - quad * 146097) * 4 + 3;
    julian += 60 + quad * 3 + extra / 146097;
    quad = julian / 1461;
    julian -= quad * 1461;
    y = julian * 4 / 1461;
    julian = ((y != 0) ? ((julian + 305) % 365) : ((julian + 306) % 366))
        + 123;
    y += quad * 4;
    *year = y - 4800;
    quad = julian * 2141 / 65536;
    *day = julian - 7834 * quad / 256;
    *month = (quad + 10) % MONTHS_PER_YEAR + 1;

    return;
}                                /* j2date() */


/*
 * j2day - convert Julian date to day-of-week (0..6 == Sun..Sat)
 *
 * Note: various places use the locution j2day(date - 1) to produce a
 * result according to the convention 0..6 = Mon..Sun.  This is a bit of
 * a crock, but will work as long as the computation here is just a modulo.
 */
int
j2day(int date)
{
    date += 1;
    date %= 7;
    /* Cope if division truncates towards zero, as it probably does */
    if (date < 0)
        date += 7;

    return date;
}                                /* j2day() */


/*
 * GetCurrentDateTime()
 *
 * Get the transaction start time ("now()") broken down as a struct pg_tm.
 */
void
GetCurrentDateTime(struct pg_tm *tm)
{
    int            tz;
    fsec_t        fsec;

    (void) timestamp2tm(GetCurrentTransactionStartTimestamp(), &tz, tm, &fsec,
                 NULL, NULL);
    /* Note: don't pass NULL tzp to timestamp2tm; affects behavior */
}

/*
 * GetCurrentTimeUsec()
 *
 * Get the transaction start time ("now()") broken down as a struct pg_tm,
 * including fractional seconds and timezone offset.
 */
void
GetCurrentTimeUsec(struct pg_tm *tm, fsec_t *fsec, int *tzp)
{
    int            tz;

    (void) timestamp2tm(GetCurrentTransactionStartTimestamp(), &tz, tm, fsec,
                 NULL, NULL);
    /* Note: don't pass NULL tzp to timestamp2tm; affects behavior */
    if (tzp != NULL)
        *tzp = tz;
}


/*
 * Append seconds and fractional seconds (if any) at *cp.
 *
 * precision is the max number of fraction digits, fillzeros says to
 * pad to two integral-seconds digits.
 *
 * Returns a pointer to the new end of string.  No NUL terminator is put
 * there; callers are responsible for NUL terminating str themselves.
 *
 * Note that any sign is stripped from the input seconds values.
 */
static char *
AppendSeconds(char *cp, int sec, fsec_t fsec, int precision, bool fillzeros)
{
    Assert(precision >= 0);

    if (fillzeros)
        cp = pg_ltostr_zeropad(cp, Abs(sec), 2);
    else
        cp = pg_ltostr(cp, Abs(sec));

    /* fsec_t is just an int32 */
    if (fsec != 0)
    {
        int32        value = Abs(fsec);
        char       *end = &cp[precision + 1];
        bool        gotnonzero = false;

        *cp++ = '.';

        /*
         * Append the fractional seconds part.  Note that we don't want any
         * trailing zeros here, so since we're building the number in reverse
         * we'll skip appending zeros until we've output a non-zero digit.
         */
        while (precision--)
        {
            int32        oldval = value;
            int32        remainder;

            value /= 10;
            remainder = oldval - value * 10;

            /* check if we got a non-zero */
            if (remainder)
                gotnonzero = true;

            if (gotnonzero)
                cp[precision] = '0' + remainder;
            else
                end = &cp[precision];
        }

        /*
         * If we still have a non-zero value then precision must have not been
         * enough to print the number.  We punt the problem to pg_ltostr(),
         * which will generate a correct answer in the minimum valid width.
         */
        if (value)
            return pg_ltostr(cp, Abs(fsec));

        return end;
    }
    else
        return cp;
}


/*
 * Variant of above that's specialized to timestamp case.
 *
 * Returns a pointer to the new end of string.  No NUL terminator is put
 * there; callers are responsible for NUL terminating str themselves.
 */
static char *
AppendTimestampSeconds(char *cp, struct pg_tm *tm, fsec_t fsec)
{
    return AppendSeconds(cp, tm->tm_sec, fsec, MAX_TIMESTAMP_PRECISION, true);
}

/*
 * Multiply frac by scale (to produce seconds) and add to *tm & *fsec.
 * We assume the input frac is less than 1 so overflow is not an issue.
 */
static void
AdjustFractSeconds(double frac, struct pg_tm *tm, fsec_t *fsec, int scale)
{
    int            sec;

    if (frac == 0)
        return;
    frac *= scale;
    sec = (int) frac;
    tm->tm_sec += sec;
    frac -= sec;
    *fsec += rint(frac * 1000000);
}

/* As above, but initial scale produces days */
static void
AdjustFractDays(double frac, struct pg_tm *tm, fsec_t *fsec, int scale)
{
    int            extra_days;

    if (frac == 0)
        return;
    frac *= scale;
    extra_days = (int) frac;
    tm->tm_mday += extra_days;
    frac -= extra_days;
    AdjustFractSeconds(frac, tm, fsec, SECS_PER_DAY);
}

/* Fetch a fractional-second value with suitable error checking */
static int
ParseFractionalSecond(char *cp, fsec_t *fsec)
{
    double        frac;

    /* Caller should always pass the start of the fraction part */
    Assert(*cp == '.');
    errno = 0;
    frac = strtod(cp, &cp);
    /* check for parse failure */
    if (*cp != '\0' || errno != 0)
        return DTERR_BAD_FORMAT;
    *fsec = rint(frac * 1000000);
    return 0;
}


/* ParseDateTime()
 *    Break string into tokens based on a date/time context.
 *    Returns 0 if successful, DTERR code if bogus input detected.
 *
 * timestr - the input string
 * workbuf - workspace for field string storage. This must be
 *     larger than the largest legal input for this datetime type --
 *     some additional space will be needed to NUL terminate fields.
 * buflen - the size of workbuf
 * field[] - pointers to field strings are returned in this array
 * ftype[] - field type indicators are returned in this array
 * maxfields - dimensions of the above two arrays
 * *numfields - set to the actual number of fields detected
 *
 * The fields extracted from the input are stored as separate,
 * null-terminated strings in the workspace at workbuf. Any text is
 * converted to lower case.
 *
 * Several field types are assigned:
 *    DTK_NUMBER - digits and (possibly) a decimal point
 *    DTK_DATE - digits and two delimiters, or digits and text
 *    DTK_TIME - digits, colon delimiters, and possibly a decimal point
 *    DTK_STRING - text (no digits or punctuation)
 *    DTK_SPECIAL - leading "+" or "-" followed by text
 *    DTK_TZ - leading "+" or "-" followed by digits (also eats ':', '.', '-')
 *
 * Note that some field types can hold unexpected items:
 *    DTK_NUMBER can hold date fields (yy.ddd)
 *    DTK_STRING can hold months (January) and time zones (PST)
 *    DTK_DATE can hold time zone names (America/New_York, GMT-8)
 */
int
ParseDateTime(const char *timestr, char *workbuf, size_t buflen,
              char **field, int *ftype, int maxfields, int *numfields)
{// #lizard forgives
    int            nf = 0;
    const char *cp = timestr;
    char       *bufp = workbuf;
    const char *bufend = workbuf + buflen;

    /*
     * Set the character pointed-to by "bufptr" to "newchar", and increment
     * "bufptr". "end" gives the end of the buffer -- we return an error if
     * there is no space left to append a character to the buffer. Note that
     * "bufptr" is evaluated twice.
     */
#define APPEND_CHAR(bufptr, end, newchar)        \
    do                                            \
    {                                            \
        if (((bufptr) + 1) >= (end))            \
            return DTERR_BAD_FORMAT;            \
        *(bufptr)++ = newchar;                    \
    } while (0)

    /* outer loop through fields */
    while (*cp != '\0')
    {
        /* Ignore spaces between fields */
        if (isspace((unsigned char) *cp))
        {
            cp++;
            continue;
        }

        /* Record start of current field */
        if (nf >= maxfields)
            return DTERR_BAD_FORMAT;
        field[nf] = bufp;

        /* leading digit? then date or time */
        if (isdigit((unsigned char) *cp))
        {
            APPEND_CHAR(bufp, bufend, *cp++);
            while (isdigit((unsigned char) *cp))
                APPEND_CHAR(bufp, bufend, *cp++);

            /* time field? */
            if (*cp == ':')
            {
                ftype[nf] = DTK_TIME;
                APPEND_CHAR(bufp, bufend, *cp++);
                while (isdigit((unsigned char) *cp) ||
                       (*cp == ':') || (*cp == '.'))
                    APPEND_CHAR(bufp, bufend, *cp++);
            }
            /* date field? allow embedded text month */
            else if (*cp == '-' || *cp == '/' || *cp == '.')
            {
                /* save delimiting character to use later */
                char        delim = *cp;

                APPEND_CHAR(bufp, bufend, *cp++);
                /* second field is all digits? then no embedded text month */
                if (isdigit((unsigned char) *cp))
                {
                    ftype[nf] = ((delim == '.') ? DTK_NUMBER : DTK_DATE);
                    while (isdigit((unsigned char) *cp))
                        APPEND_CHAR(bufp, bufend, *cp++);

                    /*
                     * insist that the delimiters match to get a three-field
                     * date.
                     */
                    if (*cp == delim)
                    {
                        ftype[nf] = DTK_DATE;
                        APPEND_CHAR(bufp, bufend, *cp++);
                        while (isdigit((unsigned char) *cp) || *cp == delim)
                            APPEND_CHAR(bufp, bufend, *cp++);
                    }
                }
                else
                {
                    ftype[nf] = DTK_DATE;
                    while (isalnum((unsigned char) *cp) || *cp == delim)
                        APPEND_CHAR(bufp, bufend, pg_tolower((unsigned char) *cp++));
                }
            }

            /*
             * otherwise, number only and will determine year, month, day, or
             * concatenated fields later...
             */
            else
                ftype[nf] = DTK_NUMBER;
        }
        /* Leading decimal point? Then fractional seconds... */
        else if (*cp == '.')
        {
            APPEND_CHAR(bufp, bufend, *cp++);
            while (isdigit((unsigned char) *cp))
                APPEND_CHAR(bufp, bufend, *cp++);

            ftype[nf] = DTK_NUMBER;
        }

        /*
         * text? then date string, month, day of week, special, or timezone
         */
        else if (isalpha((unsigned char) *cp))
        {
            bool        is_date;

            ftype[nf] = DTK_STRING;
            APPEND_CHAR(bufp, bufend, pg_tolower((unsigned char) *cp++));
            while (isalpha((unsigned char) *cp))
                APPEND_CHAR(bufp, bufend, pg_tolower((unsigned char) *cp++));

            /*
             * Dates can have embedded '-', '/', or '.' separators.  It could
             * also be a timezone name containing embedded '/', '+', '-', '_',
             * or ':' (but '_' or ':' can't be the first punctuation). If the
             * next character is a digit or '+', we need to check whether what
             * we have so far is a recognized non-timezone keyword --- if so,
             * don't believe that this is the start of a timezone.
             */
            is_date = false;
            if (*cp == '-' || *cp == '/' || *cp == '.')
                is_date = true;
            else if (*cp == '+' || isdigit((unsigned char) *cp))
            {
                *bufp = '\0';    /* null-terminate current field value */
                /* we need search only the core token table, not TZ names */
                if (datebsearch(field[nf], datetktbl, szdatetktbl) == NULL)
                    is_date = true;
            }
            if (is_date)
            {
                ftype[nf] = DTK_DATE;
                do
                {
                    APPEND_CHAR(bufp, bufend, pg_tolower((unsigned char) *cp++));
                } while (*cp == '+' || *cp == '-' ||
                         *cp == '/' || *cp == '_' ||
                         *cp == '.' || *cp == ':' ||
                         isalnum((unsigned char) *cp));
            }
        }
        /* sign? then special or numeric timezone */
        else if (*cp == '+' || *cp == '-')
        {
            APPEND_CHAR(bufp, bufend, *cp++);
            /* soak up leading whitespace */
            while (isspace((unsigned char) *cp))
                cp++;
            /* numeric timezone? */
            /* note that "DTK_TZ" could also be a signed float or yyyy-mm */
            if (isdigit((unsigned char) *cp))
            {
                ftype[nf] = DTK_TZ;
                APPEND_CHAR(bufp, bufend, *cp++);
                while (isdigit((unsigned char) *cp) ||
                       *cp == ':' || *cp == '.' || *cp == '-')
                    APPEND_CHAR(bufp, bufend, *cp++);
            }
            /* special? */
            else if (isalpha((unsigned char) *cp))
            {
                ftype[nf] = DTK_SPECIAL;
                APPEND_CHAR(bufp, bufend, pg_tolower((unsigned char) *cp++));
                while (isalpha((unsigned char) *cp))
                    APPEND_CHAR(bufp, bufend, pg_tolower((unsigned char) *cp++));
            }
            /* otherwise something wrong... */
            else
                return DTERR_BAD_FORMAT;
        }
        /* ignore other punctuation but use as delimiter */
        else if (ispunct((unsigned char) *cp))
        {
            cp++;
            continue;
        }
        /* otherwise, something is not right... */
        else
            return DTERR_BAD_FORMAT;

        /* force in a delimiter after each field */
        *bufp++ = '\0';
        nf++;
    }

    *numfields = nf;

    return 0;
}


/* DecodeDateTime()
 * Interpret previously parsed fields for general date and time.
 * Return 0 if full date, 1 if only time, and negative DTERR code if problems.
 * (Currently, all callers treat 1 as an error return too.)
 *
 *        External format(s):
 *                "<weekday> <month>-<day>-<year> <hour>:<minute>:<second>"
 *                "Fri Feb-7-1997 15:23:27"
 *                "Feb-7-1997 15:23:27"
 *                "2-7-1997 15:23:27"
 *                "1997-2-7 15:23:27"
 *                "1997.038 15:23:27"        (day of year 1-366)
 *        Also supports input in compact time:
 *                "970207 152327"
 *                "97038 152327"
 *                "20011225T040506.789-07"
 *
 * Use the system-provided functions to get the current time zone
 * if not specified in the input string.
 *
 * If the date is outside the range of pg_time_t (in practice that could only
 * happen if pg_time_t is just 32 bits), then assume UTC time zone - thomas
 * 1997-05-27
 */
int
DecodeDateTime(char **field, int *ftype, int nf,
               int *dtype, struct pg_tm *tm, fsec_t *fsec, int *tzp)
{// #lizard forgives
    int            fmask = 0,
                tmask,
                type;
    int            ptype = 0;        /* "prefix type" for ISO y2001m02d04 format */
    int            i;
    int            val;
    int            dterr;
    int            mer = HR24;
    bool        haveTextMonth = FALSE;
    bool        isjulian = FALSE;
    bool        is2digits = FALSE;
    bool        bc = FALSE;
    pg_tz       *namedTz = NULL;
    pg_tz       *abbrevTz = NULL;
    pg_tz       *valtz;
    char       *abbrev = NULL;
    struct pg_tm cur_tm;

    /*
     * We'll insist on at least all of the date fields, but initialize the
     * remaining fields in case they are not set later...
     */
    *dtype = DTK_DATE;
    tm->tm_hour = 0;
    tm->tm_min = 0;
    tm->tm_sec = 0;
    *fsec = 0;
    /* don't know daylight savings time status apriori */
    tm->tm_isdst = -1;
    if (tzp != NULL)
        *tzp = 0;

    for (i = 0; i < nf; i++)
    {
        switch (ftype[i])
        {
            case DTK_DATE:

                /*
                 * Integral julian day with attached time zone? All other
                 * forms with JD will be separated into distinct fields, so we
                 * handle just this case here.
                 */
                if (ptype == DTK_JULIAN)
                {
                    char       *cp;
                    int            val;

                    if (tzp == NULL)
                        return DTERR_BAD_FORMAT;

                    errno = 0;
                    val = strtoint(field[i], &cp, 10);
                    if (errno == ERANGE || val < 0)
                        return DTERR_FIELD_OVERFLOW;

                    j2date(val, &tm->tm_year, &tm->tm_mon, &tm->tm_mday);
                    isjulian = TRUE;

                    /* Get the time zone from the end of the string */
                    dterr = DecodeTimezone(cp, tzp);
                    if (dterr)
                        return dterr;

                    tmask = DTK_DATE_M | DTK_TIME_M | DTK_M(TZ);
                    ptype = 0;
                    break;
                }

                /*
                 * Already have a date? Then this might be a time zone name
                 * with embedded punctuation (e.g. "America/New_York") or a
                 * run-together time with trailing time zone (e.g. hhmmss-zz).
                 * - thomas 2001-12-25
                 *
                 * We consider it a time zone if we already have month & day.
                 * This is to allow the form "mmm dd hhmmss tz year", which
                 * we've historically accepted.
                 */
                else if (ptype != 0 ||
                         ((fmask & (DTK_M(MONTH) | DTK_M(DAY))) ==
                          (DTK_M(MONTH) | DTK_M(DAY))))
                {
                    /* No time zone accepted? Then quit... */
                    if (tzp == NULL)
                        return DTERR_BAD_FORMAT;

                    if (isdigit((unsigned char) *field[i]) || ptype != 0)
                    {
                        char       *cp;

                        if (ptype != 0)
                        {
                            /* Sanity check; should not fail this test */
                            if (ptype != DTK_TIME)
                                return DTERR_BAD_FORMAT;
                            ptype = 0;
                        }

                        /*
                         * Starts with a digit but we already have a time
                         * field? Then we are in trouble with a date and time
                         * already...
                         */
                        if ((fmask & DTK_TIME_M) == DTK_TIME_M)
                            return DTERR_BAD_FORMAT;

                        if ((cp = strchr(field[i], '-')) == NULL)
                            return DTERR_BAD_FORMAT;

                        /* Get the time zone from the end of the string */
                        dterr = DecodeTimezone(cp, tzp);
                        if (dterr)
                            return dterr;
                        *cp = '\0';

                        /*
                         * Then read the rest of the field as a concatenated
                         * time
                         */
                        dterr = DecodeNumberField(strlen(field[i]), field[i],
                                                  fmask,
                                                  &tmask, tm,
                                                  fsec, &is2digits);
                        if (dterr < 0)
                            return dterr;

                        /*
                         * modify tmask after returning from
                         * DecodeNumberField()
                         */
                        tmask |= DTK_M(TZ);
                    }
                    else
                    {
                        namedTz = pg_tzset(field[i]);
                        if (!namedTz)
                        {
                            /*
                             * We should return an error code instead of
                             * ereport'ing directly, but then there is no way
                             * to report the bad time zone name.
                             */
                            ereport(ERROR,
                                    (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                                     errmsg("time zone \"%s\" not recognized",
                                            field[i])));
                        }
                        /* we'll apply the zone setting below */
                        tmask = DTK_M(TZ);
                    }
                }
                else
                {
                    dterr = DecodeDate(field[i], fmask,
                                       &tmask, &is2digits, tm);
                    if (dterr)
                        return dterr;
                }
                break;

            case DTK_TIME:

                /*
                 * This might be an ISO time following a "t" field.
                 */
                if (ptype != 0)
                {
                    /* Sanity check; should not fail this test */
                    if (ptype != DTK_TIME)
                        return DTERR_BAD_FORMAT;
                    ptype = 0;
                }
                dterr = DecodeTime(field[i], fmask, INTERVAL_FULL_RANGE,
                                   &tmask, tm, fsec);
                if (dterr)
                    return dterr;

                /*
                 * Check upper limit on hours; other limits checked in
                 * DecodeTime()
                 */
                /* test for > 24:00:00 */
                if (tm->tm_hour > HOURS_PER_DAY ||
                    (tm->tm_hour == HOURS_PER_DAY &&
                     (tm->tm_min > 0 || tm->tm_sec > 0 || *fsec > 0)))
                    return DTERR_FIELD_OVERFLOW;
                break;

            case DTK_TZ:
                {
                    int            tz;

                    if (tzp == NULL)
                        return DTERR_BAD_FORMAT;

                    dterr = DecodeTimezone(field[i], &tz);
                    if (dterr)
                        return dterr;
                    *tzp = tz;
                    tmask = DTK_M(TZ);
                }
                break;

            case DTK_NUMBER:

                /*
                 * Was this an "ISO date" with embedded field labels? An
                 * example is "y2001m02d04" - thomas 2001-02-04
                 */
                if (ptype != 0)
                {
                    char       *cp;
                    int            val;

                    errno = 0;
                    val = strtoint(field[i], &cp, 10);
                    if (errno == ERANGE)
                        return DTERR_FIELD_OVERFLOW;

                    /*
                     * only a few kinds are allowed to have an embedded
                     * decimal
                     */
                    if (*cp == '.')
                        switch (ptype)
                        {
                            case DTK_JULIAN:
                            case DTK_TIME:
                            case DTK_SECOND:
                                break;
                            default:
                                return DTERR_BAD_FORMAT;
                                break;
                        }
                    else if (*cp != '\0')
                        return DTERR_BAD_FORMAT;

                    switch (ptype)
                    {
                        case DTK_YEAR:
                            tm->tm_year = val;
                            tmask = DTK_M(YEAR);
                            break;

                        case DTK_MONTH:

                            /*
                             * already have a month and hour? then assume
                             * minutes
                             */
                            if ((fmask & DTK_M(MONTH)) != 0 &&
                                (fmask & DTK_M(HOUR)) != 0)
                            {
                                tm->tm_min = val;
                                tmask = DTK_M(MINUTE);
                            }
                            else
                            {
                                tm->tm_mon = val;
                                tmask = DTK_M(MONTH);
                            }
                            break;

                        case DTK_DAY:
                            tm->tm_mday = val;
                            tmask = DTK_M(DAY);
                            break;

                        case DTK_HOUR:
                            tm->tm_hour = val;
                            tmask = DTK_M(HOUR);
                            break;

                        case DTK_MINUTE:
                            tm->tm_min = val;
                            tmask = DTK_M(MINUTE);
                            break;

                        case DTK_SECOND:
                            tm->tm_sec = val;
                            tmask = DTK_M(SECOND);
                            if (*cp == '.')
                            {
                                dterr = ParseFractionalSecond(cp, fsec);
                                if (dterr)
                                    return dterr;
                                tmask = DTK_ALL_SECS_M;
                            }
                            break;

                        case DTK_TZ:
                            tmask = DTK_M(TZ);
                            dterr = DecodeTimezone(field[i], tzp);
                            if (dterr)
                                return dterr;
                            break;

                        case DTK_JULIAN:
                            /* previous field was a label for "julian date" */
                            if (val < 0)
                                return DTERR_FIELD_OVERFLOW;
                            tmask = DTK_DATE_M;
                            j2date(val, &tm->tm_year, &tm->tm_mon, &tm->tm_mday);
                            isjulian = TRUE;

                            /* fractional Julian Day? */
                            if (*cp == '.')
                            {
                                double        time;

                                errno = 0;
                                time = strtod(cp, &cp);
                                if (*cp != '\0' || errno != 0)
                                    return DTERR_BAD_FORMAT;
                                time *= USECS_PER_DAY;
                                dt2time(time,
                                        &tm->tm_hour, &tm->tm_min,
                                        &tm->tm_sec, fsec);
                                tmask |= DTK_TIME_M;
                            }
                            break;

                        case DTK_TIME:
                            /* previous field was "t" for ISO time */
                            dterr = DecodeNumberField(strlen(field[i]), field[i],
                                                      (fmask | DTK_DATE_M),
                                                      &tmask, tm,
                                                      fsec, &is2digits);
                            if (dterr < 0)
                                return dterr;
                            if (tmask != DTK_TIME_M)
                                return DTERR_BAD_FORMAT;
                            break;

                        default:
                            return DTERR_BAD_FORMAT;
                            break;
                    }

                    ptype = 0;
                    *dtype = DTK_DATE;
                }
                else
                {
                    char       *cp;
                    int            flen;

                    flen = strlen(field[i]);
                    cp = strchr(field[i], '.');

                    /* Embedded decimal and no date yet? */
                    if (cp != NULL && !(fmask & DTK_DATE_M))
                    {
                        dterr = DecodeDate(field[i], fmask,
                                           &tmask, &is2digits, tm);
                        if (dterr)
                            return dterr;
                    }
                    /* embedded decimal and several digits before? */
                    else if (cp != NULL && flen - strlen(cp) > 2)
                    {
                        /*
                         * Interpret as a concatenated date or time Set the
                         * type field to allow decoding other fields later.
                         * Example: 20011223 or 040506
                         */
                        dterr = DecodeNumberField(flen, field[i], fmask,
                                                  &tmask, tm,
                                                  fsec, &is2digits);
                        if (dterr < 0)
                            return dterr;
                    }

                    /*
                     * Is this a YMD or HMS specification, or a year number?
                     * YMD and HMS are required to be six digits or more, so
                     * if it is 5 digits, it is a year.  If it is six or more
                     * more digits, we assume it is YMD or HMS unless no date
                     * and no time values have been specified.  This forces 6+
                     * digit years to be at the end of the string, or to use
                     * the ISO date specification.
                     */
                    else if (flen >= 6 && (!(fmask & DTK_DATE_M) ||
                                           !(fmask & DTK_TIME_M)))
                    {
                        dterr = DecodeNumberField(flen, field[i], fmask,
                                                  &tmask, tm,
                                                  fsec, &is2digits);
                        if (dterr < 0)
                            return dterr;
                    }
                    /* otherwise it is a single date/time field... */
                    else
                    {
                        dterr = DecodeNumber(flen, field[i],
                                             haveTextMonth, fmask,
                                             &tmask, tm,
                                             fsec, &is2digits);
                        if (dterr)
                            return dterr;
                    }
                }
                break;

            case DTK_STRING:
            case DTK_SPECIAL:
                /* timezone abbrevs take precedence over built-in tokens */
                type = DecodeTimezoneAbbrev(i, field[i], &val, &valtz);
                if (type == UNKNOWN_FIELD)
                    type = DecodeSpecial(i, field[i], &val);
                if (type == IGNORE_DTF)
                    continue;

                tmask = DTK_M(type);
                switch (type)
                {
                    case RESERV:
                        switch (val)
                        {
                            case DTK_CURRENT:
                                ereport(ERROR,
                                        (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                                         errmsg("date/time value \"current\" is no longer supported")));

                                return DTERR_BAD_FORMAT;
                                break;

                            case DTK_NOW:
                                tmask = (DTK_DATE_M | DTK_TIME_M | DTK_M(TZ));
                                *dtype = DTK_DATE;
                                GetCurrentTimeUsec(tm, fsec, tzp);
                                break;

                            case DTK_YESTERDAY:
                                tmask = DTK_DATE_M;
                                *dtype = DTK_DATE;
                                GetCurrentDateTime(&cur_tm);
                                j2date(date2j(cur_tm.tm_year, cur_tm.tm_mon, cur_tm.tm_mday) - 1,
                                       &tm->tm_year, &tm->tm_mon, &tm->tm_mday);
                                break;

                            case DTK_TODAY:
                                tmask = DTK_DATE_M;
                                *dtype = DTK_DATE;
                                GetCurrentDateTime(&cur_tm);
                                tm->tm_year = cur_tm.tm_year;
                                tm->tm_mon = cur_tm.tm_mon;
                                tm->tm_mday = cur_tm.tm_mday;
                                break;

                            case DTK_TOMORROW:
                                tmask = DTK_DATE_M;
                                *dtype = DTK_DATE;
                                GetCurrentDateTime(&cur_tm);
                                j2date(date2j(cur_tm.tm_year, cur_tm.tm_mon, cur_tm.tm_mday) + 1,
                                       &tm->tm_year, &tm->tm_mon, &tm->tm_mday);
                                break;

                            case DTK_ZULU:
                                tmask = (DTK_TIME_M | DTK_M(TZ));
                                *dtype = DTK_DATE;
                                tm->tm_hour = 0;
                                tm->tm_min = 0;
                                tm->tm_sec = 0;
                                if (tzp != NULL)
                                    *tzp = 0;
                                break;

                            default:
                                *dtype = val;
                        }

                        break;

                    case MONTH:

                        /*
                         * already have a (numeric) month? then see if we can
                         * substitute...
                         */
                        if ((fmask & DTK_M(MONTH)) && !haveTextMonth &&
                            !(fmask & DTK_M(DAY)) && tm->tm_mon >= 1 &&
                            tm->tm_mon <= 31)
                        {
                            tm->tm_mday = tm->tm_mon;
                            tmask = DTK_M(DAY);
                        }
                        haveTextMonth = TRUE;
                        tm->tm_mon = val;
                        break;

                    case DTZMOD:

                        /*
                         * daylight savings time modifier (solves "MET DST"
                         * syntax)
                         */
                        tmask |= DTK_M(DTZ);
                        tm->tm_isdst = 1;
                        if (tzp == NULL)
                            return DTERR_BAD_FORMAT;
                        *tzp -= val;
                        break;

                    case DTZ:

                        /*
                         * set mask for TZ here _or_ check for DTZ later when
                         * getting default timezone
                         */
                        tmask |= DTK_M(TZ);
                        tm->tm_isdst = 1;
                        if (tzp == NULL)
                            return DTERR_BAD_FORMAT;
                        *tzp = -val;
                        break;

                    case TZ:
                        tm->tm_isdst = 0;
                        if (tzp == NULL)
                            return DTERR_BAD_FORMAT;
                        *tzp = -val;
                        break;

                    case DYNTZ:
                        tmask |= DTK_M(TZ);
                        if (tzp == NULL)
                            return DTERR_BAD_FORMAT;
                        /* we'll determine the actual offset later */
                        abbrevTz = valtz;
                        abbrev = field[i];
                        break;

                    case AMPM:
                        mer = val;
                        break;

                    case ADBC:
                        bc = (val == BC);
                        break;

                    case DOW:
                        tm->tm_wday = val;
                        break;

                    case UNITS:
                        tmask = 0;
                        ptype = val;
                        break;

                    case ISOTIME:

                        /*
                         * This is a filler field "t" indicating that the next
                         * field is time. Try to verify that this is sensible.
                         */
                        tmask = 0;

                        /* No preceding date? Then quit... */
                        if ((fmask & DTK_DATE_M) != DTK_DATE_M)
                            return DTERR_BAD_FORMAT;

                        /***
                         * We will need one of the following fields:
                         *    DTK_NUMBER should be hhmmss.fff
                         *    DTK_TIME should be hh:mm:ss.fff
                         *    DTK_DATE should be hhmmss-zz
                         ***/
                        if (i >= nf - 1 ||
                            (ftype[i + 1] != DTK_NUMBER &&
                             ftype[i + 1] != DTK_TIME &&
                             ftype[i + 1] != DTK_DATE))
                            return DTERR_BAD_FORMAT;

                        ptype = val;
                        break;

                    case UNKNOWN_FIELD:

                        /*
                         * Before giving up and declaring error, check to see
                         * if it is an all-alpha timezone name.
                         */
                        namedTz = pg_tzset(field[i]);
                        if (!namedTz)
                            return DTERR_BAD_FORMAT;
                        /* we'll apply the zone setting below */
                        tmask = DTK_M(TZ);
                        break;

                    default:
                        return DTERR_BAD_FORMAT;
                }
                break;

            default:
                return DTERR_BAD_FORMAT;
        }

        if (tmask & fmask)
            return DTERR_BAD_FORMAT;
        fmask |= tmask;
    }                            /* end loop over fields */

    /* do final checking/adjustment of Y/M/D fields */
    dterr = ValidateDate(fmask, isjulian, is2digits, bc, tm);
    if (dterr)
        return dterr;

    /* handle AM/PM */
    if (mer != HR24 && tm->tm_hour > HOURS_PER_DAY / 2)
        return DTERR_FIELD_OVERFLOW;
    if (mer == AM && tm->tm_hour == HOURS_PER_DAY / 2)
        tm->tm_hour = 0;
    else if (mer == PM && tm->tm_hour != HOURS_PER_DAY / 2)
        tm->tm_hour += HOURS_PER_DAY / 2;

    /* do additional checking for full date specs... */
    if (*dtype == DTK_DATE)
    {
        if ((fmask & DTK_DATE_M) != DTK_DATE_M)
        {
            if ((fmask & DTK_TIME_M) == DTK_TIME_M)
                return 1;
            return DTERR_BAD_FORMAT;
        }

        /*
         * If we had a full timezone spec, compute the offset (we could not do
         * it before, because we need the date to resolve DST status).
         */
        if (namedTz != NULL)
        {
            /* daylight savings time modifier disallowed with full TZ */
            if (fmask & DTK_M(DTZMOD))
                return DTERR_BAD_FORMAT;

            *tzp = DetermineTimeZoneOffset(tm, namedTz);
        }

        /*
         * Likewise, if we had a dynamic timezone abbreviation, resolve it
         * now.
         */
        if (abbrevTz != NULL)
        {
            /* daylight savings time modifier disallowed with dynamic TZ */
            if (fmask & DTK_M(DTZMOD))
                return DTERR_BAD_FORMAT;

            *tzp = DetermineTimeZoneAbbrevOffset(tm, abbrev, abbrevTz);
        }

        /* timezone not specified? then use session timezone */
        if (tzp != NULL && !(fmask & DTK_M(TZ)))
        {
            /*
             * daylight savings time modifier but no standard timezone? then
             * error
             */
            if (fmask & DTK_M(DTZMOD))
                return DTERR_BAD_FORMAT;

            *tzp = DetermineTimeZoneOffset(tm, session_timezone);
        }
    }

    return 0;
}


/* DetermineTimeZoneOffset()
 *
 * Given a struct pg_tm in which tm_year, tm_mon, tm_mday, tm_hour, tm_min,
 * and tm_sec fields are set, and a zic-style time zone definition, determine
 * the applicable GMT offset and daylight-savings status at that time.
 * Set the struct pg_tm's tm_isdst field accordingly, and return the GMT
 * offset as the function result.
 *
 * Note: if the date is out of the range we can deal with, we return zero
 * as the GMT offset and set tm_isdst = 0.  We don't throw an error here,
 * though probably some higher-level code will.
 */
int
DetermineTimeZoneOffset(struct pg_tm *tm, pg_tz *tzp)
{
    pg_time_t    t;

    return DetermineTimeZoneOffsetInternal(tm, tzp, &t);
}


/* DetermineTimeZoneOffsetInternal()
 *
 * As above, but also return the actual UTC time imputed to the date/time
 * into *tp.
 *
 * In event of an out-of-range date, we punt by returning zero into *tp.
 * This is okay for the immediate callers but is a good reason for not
 * exposing this worker function globally.
 *
 * Note: it might seem that we should use mktime() for this, but bitter
 * experience teaches otherwise.  This code is much faster than most versions
 * of mktime(), anyway.
 */
static int
DetermineTimeZoneOffsetInternal(struct pg_tm *tm, pg_tz *tzp, pg_time_t *tp)
{// #lizard forgives
    int            date,
                sec;
    pg_time_t    day,
                mytime,
                prevtime,
                boundary,
                beforetime,
                aftertime;
    long int    before_gmtoff,
                after_gmtoff;
    int            before_isdst,
                after_isdst;
    int            res;

    /*
     * First, generate the pg_time_t value corresponding to the given
     * y/m/d/h/m/s taken as GMT time.  If this overflows, punt and decide the
     * timezone is GMT.  (For a valid Julian date, integer overflow should be
     * impossible with 64-bit pg_time_t, but let's check for safety.)
     */
    if (!IS_VALID_JULIAN(tm->tm_year, tm->tm_mon, tm->tm_mday))
        goto overflow;
    date = date2j(tm->tm_year, tm->tm_mon, tm->tm_mday) - UNIX_EPOCH_JDATE;

    day = ((pg_time_t) date) * SECS_PER_DAY;
    if (day / SECS_PER_DAY != date)
        goto overflow;
    sec = tm->tm_sec + (tm->tm_min + tm->tm_hour * MINS_PER_HOUR) * SECS_PER_MINUTE;
    mytime = day + sec;
    /* since sec >= 0, overflow could only be from +day to -mytime */
    if (mytime < 0 && day > 0)
        goto overflow;

    /*
     * Find the DST time boundary just before or following the target time. We
     * assume that all zones have GMT offsets less than 24 hours, and that DST
     * boundaries can't be closer together than 48 hours, so backing up 24
     * hours and finding the "next" boundary will work.
     */
    prevtime = mytime - SECS_PER_DAY;
    if (mytime < 0 && prevtime > 0)
        goto overflow;

    res = pg_next_dst_boundary(&prevtime,
                               &before_gmtoff, &before_isdst,
                               &boundary,
                               &after_gmtoff, &after_isdst,
                               tzp);
    if (res < 0)
        goto overflow;            /* failure? */

    if (res == 0)
    {
        /* Non-DST zone, life is simple */
        tm->tm_isdst = before_isdst;
        *tp = mytime - before_gmtoff;
        return -(int) before_gmtoff;
    }

    /*
     * Form the candidate pg_time_t values with local-time adjustment
     */
    beforetime = mytime - before_gmtoff;
    if ((before_gmtoff > 0 &&
         mytime < 0 && beforetime > 0) ||
        (before_gmtoff <= 0 &&
         mytime > 0 && beforetime < 0))
        goto overflow;
    aftertime = mytime - after_gmtoff;
    if ((after_gmtoff > 0 &&
         mytime < 0 && aftertime > 0) ||
        (after_gmtoff <= 0 &&
         mytime > 0 && aftertime < 0))
        goto overflow;

    /*
     * If both before or both after the boundary time, we know what to do. The
     * boundary time itself is considered to be after the transition, which
     * means we can accept aftertime == boundary in the second case.
     */
    if (beforetime < boundary && aftertime < boundary)
    {
        tm->tm_isdst = before_isdst;
        *tp = beforetime;
        return -(int) before_gmtoff;
    }
    if (beforetime > boundary && aftertime >= boundary)
    {
        tm->tm_isdst = after_isdst;
        *tp = aftertime;
        return -(int) after_gmtoff;
    }

    /*
     * It's an invalid or ambiguous time due to timezone transition.  In a
     * spring-forward transition, prefer the "before" interpretation; in a
     * fall-back transition, prefer "after".  (We used to define and implement
     * this test as "prefer the standard-time interpretation", but that rule
     * does not help to resolve the behavior when both times are reported as
     * standard time; which does happen, eg Europe/Moscow in Oct 2014.)
     */
    if (beforetime > aftertime)
    {
        tm->tm_isdst = before_isdst;
        *tp = beforetime;
        return -(int) before_gmtoff;
    }
    tm->tm_isdst = after_isdst;
    *tp = aftertime;
    return -(int) after_gmtoff;

overflow:
    /* Given date is out of range, so assume UTC */
    tm->tm_isdst = 0;
    *tp = 0;
    return 0;
}


/* DetermineTimeZoneAbbrevOffset()
 *
 * Determine the GMT offset and DST flag to be attributed to a dynamic
 * time zone abbreviation, that is one whose meaning has changed over time.
 * *tm contains the local time at which the meaning should be determined,
 * and tm->tm_isdst receives the DST flag.
 *
 * This differs from the behavior of DetermineTimeZoneOffset() in that a
 * standard-time or daylight-time abbreviation forces use of the corresponding
 * GMT offset even when the zone was then in DS or standard time respectively.
 * (However, that happens only if we can match the given abbreviation to some
 * abbreviation that appears in the IANA timezone data.  Otherwise, we fall
 * back to doing DetermineTimeZoneOffset().)
 */
int
DetermineTimeZoneAbbrevOffset(struct pg_tm *tm, const char *abbr, pg_tz *tzp)
{
    pg_time_t    t;
    int            zone_offset;
    int            abbr_offset;
    int            abbr_isdst;

    /*
     * Compute the UTC time we want to probe at.  (In event of overflow, we'll
     * probe at the epoch, which is a bit random but probably doesn't matter.)
     */
    zone_offset = DetermineTimeZoneOffsetInternal(tm, tzp, &t);

    /*
     * Try to match the abbreviation to something in the zone definition.
     */
    if (DetermineTimeZoneAbbrevOffsetInternal(t, abbr, tzp,
                                              &abbr_offset, &abbr_isdst))
    {
        /* Success, so use the abbrev-specific answers. */
        tm->tm_isdst = abbr_isdst;
        return abbr_offset;
    }

    /*
     * No match, so use the answers we already got from
     * DetermineTimeZoneOffsetInternal.
     */
    return zone_offset;
}


/* DetermineTimeZoneAbbrevOffsetTS()
 *
 * As above but the probe time is specified as a TimestampTz (hence, UTC time),
 * and DST status is returned into *isdst rather than into tm->tm_isdst.
 */
int
DetermineTimeZoneAbbrevOffsetTS(TimestampTz ts, const char *abbr,
                                pg_tz *tzp, int *isdst)
{
    pg_time_t    t = timestamptz_to_time_t(ts);
    int            zone_offset;
    int            abbr_offset;
    int            tz;
    struct pg_tm tm;
    fsec_t        fsec;

    /*
     * If the abbrev matches anything in the zone data, this is pretty easy.
     */
    if (DetermineTimeZoneAbbrevOffsetInternal(t, abbr, tzp,
                                              &abbr_offset, isdst))
        return abbr_offset;

    /*
     * Else, break down the timestamp so we can use DetermineTimeZoneOffset.
     */
    if (timestamp2tm(ts, &tz, &tm, &fsec, NULL, tzp) != 0)
        ereport(ERROR,
                (errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),
                 errmsg("timestamp out of range")));

    zone_offset = DetermineTimeZoneOffset(&tm, tzp);
    *isdst = tm.tm_isdst;
    return zone_offset;
}


/* DetermineTimeZoneAbbrevOffsetInternal()
 *
 * Workhorse for above two functions: work from a pg_time_t probe instant.
 * On success, return GMT offset and DST status into *offset and *isdst.
 */
static bool
DetermineTimeZoneAbbrevOffsetInternal(pg_time_t t, const char *abbr, pg_tz *tzp,
                                      int *offset, int *isdst)
{
    char        upabbr[TZ_STRLEN_MAX + 1];
    unsigned char *p;
    long int    gmtoff;

    /* We need to force the abbrev to upper case */
    strlcpy(upabbr, abbr, sizeof(upabbr));
    for (p = (unsigned char *) upabbr; *p; p++)
        *p = pg_toupper(*p);

    /* Look up the abbrev's meaning at this time in this zone */
    if (pg_interpret_timezone_abbrev(upabbr,
                                     &t,
                                     &gmtoff,
                                     isdst,
                                     tzp))
    {
        /* Change sign to agree with DetermineTimeZoneOffset() */
        *offset = (int) -gmtoff;
        return true;
    }
    return false;
}


/* DecodeTimeOnly()
 * Interpret parsed string as time fields only.
 * Returns 0 if successful, DTERR code if bogus input detected.
 *
 * Note that support for time zone is here for
 * SQL TIME WITH TIME ZONE, but it reveals
 * bogosity with SQL date/time standards, since
 * we must infer a time zone from current time.
 * - thomas 2000-03-10
 * Allow specifying date to get a better time zone,
 * if time zones are allowed. - thomas 2001-12-26
 */
int
DecodeTimeOnly(char **field, int *ftype, int nf,
               int *dtype, struct pg_tm *tm, fsec_t *fsec, int *tzp)
{// #lizard forgives
    int            fmask = 0,
                tmask,
                type;
    int            ptype = 0;        /* "prefix type" for ISO h04mm05s06 format */
    int            i;
    int            val;
    int            dterr;
    bool        isjulian = FALSE;
    bool        is2digits = FALSE;
    bool        bc = FALSE;
    int            mer = HR24;
    pg_tz       *namedTz = NULL;
    pg_tz       *abbrevTz = NULL;
    char       *abbrev = NULL;
    pg_tz       *valtz;

    *dtype = DTK_TIME;
    tm->tm_hour = 0;
    tm->tm_min = 0;
    tm->tm_sec = 0;
    *fsec = 0;
    /* don't know daylight savings time status apriori */
    tm->tm_isdst = -1;

    if (tzp != NULL)
        *tzp = 0;

    for (i = 0; i < nf; i++)
    {
        switch (ftype[i])
        {
            case DTK_DATE:

                /*
                 * Time zone not allowed? Then should not accept dates or time
                 * zones no matter what else!
                 */
                if (tzp == NULL)
                    return DTERR_BAD_FORMAT;

                /* Under limited circumstances, we will accept a date... */
                if (i == 0 && nf >= 2 &&
                    (ftype[nf - 1] == DTK_DATE || ftype[1] == DTK_TIME))
                {
                    dterr = DecodeDate(field[i], fmask,
                                       &tmask, &is2digits, tm);
                    if (dterr)
                        return dterr;
                }
                /* otherwise, this is a time and/or time zone */
                else
                {
                    if (isdigit((unsigned char) *field[i]))
                    {
                        char       *cp;

                        /*
                         * Starts with a digit but we already have a time
                         * field? Then we are in trouble with time already...
                         */
                        if ((fmask & DTK_TIME_M) == DTK_TIME_M)
                            return DTERR_BAD_FORMAT;

                        /*
                         * Should not get here and fail. Sanity check only...
                         */
                        if ((cp = strchr(field[i], '-')) == NULL)
                            return DTERR_BAD_FORMAT;

                        /* Get the time zone from the end of the string */
                        dterr = DecodeTimezone(cp, tzp);
                        if (dterr)
                            return dterr;
                        *cp = '\0';

                        /*
                         * Then read the rest of the field as a concatenated
                         * time
                         */
                        dterr = DecodeNumberField(strlen(field[i]), field[i],
                                                  (fmask | DTK_DATE_M),
                                                  &tmask, tm,
                                                  fsec, &is2digits);
                        if (dterr < 0)
                            return dterr;
                        ftype[i] = dterr;

                        tmask |= DTK_M(TZ);
                    }
                    else
                    {
                        namedTz = pg_tzset(field[i]);
                        if (!namedTz)
                        {
                            /*
                             * We should return an error code instead of
                             * ereport'ing directly, but then there is no way
                             * to report the bad time zone name.
                             */
                            ereport(ERROR,
                                    (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                                     errmsg("time zone \"%s\" not recognized",
                                            field[i])));
                        }
                        /* we'll apply the zone setting below */
                        ftype[i] = DTK_TZ;
                        tmask = DTK_M(TZ);
                    }
                }
                break;

            case DTK_TIME:
                dterr = DecodeTime(field[i], (fmask | DTK_DATE_M),
                                   INTERVAL_FULL_RANGE,
                                   &tmask, tm, fsec);
                if (dterr)
                    return dterr;
                break;

            case DTK_TZ:
                {
                    int            tz;

                    if (tzp == NULL)
                        return DTERR_BAD_FORMAT;

                    dterr = DecodeTimezone(field[i], &tz);
                    if (dterr)
                        return dterr;
                    *tzp = tz;
                    tmask = DTK_M(TZ);
                }
                break;

            case DTK_NUMBER:

                /*
                 * Was this an "ISO time" with embedded field labels? An
                 * example is "h04m05s06" - thomas 2001-02-04
                 */
                if (ptype != 0)
                {
                    char       *cp;
                    int            val;

                    /* Only accept a date under limited circumstances */
                    switch (ptype)
                    {
                        case DTK_JULIAN:
                        case DTK_YEAR:
                        case DTK_MONTH:
                        case DTK_DAY:
                            if (tzp == NULL)
                                return DTERR_BAD_FORMAT;
                        default:
                            break;
                    }

                    errno = 0;
                    val = strtoint(field[i], &cp, 10);
                    if (errno == ERANGE)
                        return DTERR_FIELD_OVERFLOW;

                    /*
                     * only a few kinds are allowed to have an embedded
                     * decimal
                     */
                    if (*cp == '.')
                        switch (ptype)
                        {
                            case DTK_JULIAN:
                            case DTK_TIME:
                            case DTK_SECOND:
                                break;
                            default:
                                return DTERR_BAD_FORMAT;
                                break;
                        }
                    else if (*cp != '\0')
                        return DTERR_BAD_FORMAT;

                    switch (ptype)
                    {
                        case DTK_YEAR:
                            tm->tm_year = val;
                            tmask = DTK_M(YEAR);
                            break;

                        case DTK_MONTH:

                            /*
                             * already have a month and hour? then assume
                             * minutes
                             */
                            if ((fmask & DTK_M(MONTH)) != 0 &&
                                (fmask & DTK_M(HOUR)) != 0)
                            {
                                tm->tm_min = val;
                                tmask = DTK_M(MINUTE);
                            }
                            else
                            {
                                tm->tm_mon = val;
                                tmask = DTK_M(MONTH);
                            }
                            break;

                        case DTK_DAY:
                            tm->tm_mday = val;
                            tmask = DTK_M(DAY);
                            break;

                        case DTK_HOUR:
                            tm->tm_hour = val;
                            tmask = DTK_M(HOUR);
                            break;

                        case DTK_MINUTE:
                            tm->tm_min = val;
                            tmask = DTK_M(MINUTE);
                            break;

                        case DTK_SECOND:
                            tm->tm_sec = val;
                            tmask = DTK_M(SECOND);
                            if (*cp == '.')
                            {
                                dterr = ParseFractionalSecond(cp, fsec);
                                if (dterr)
                                    return dterr;
                                tmask = DTK_ALL_SECS_M;
                            }
                            break;

                        case DTK_TZ:
                            tmask = DTK_M(TZ);
                            dterr = DecodeTimezone(field[i], tzp);
                            if (dterr)
                                return dterr;
                            break;

                        case DTK_JULIAN:
                            /* previous field was a label for "julian date" */
                            if (val < 0)
                                return DTERR_FIELD_OVERFLOW;
                            tmask = DTK_DATE_M;
                            j2date(val, &tm->tm_year, &tm->tm_mon, &tm->tm_mday);
                            isjulian = TRUE;

                            if (*cp == '.')
                            {
                                double        time;

                                errno = 0;
                                time = strtod(cp, &cp);
                                if (*cp != '\0' || errno != 0)
                                    return DTERR_BAD_FORMAT;
                                time *= USECS_PER_DAY;
                                dt2time(time,
                                        &tm->tm_hour, &tm->tm_min,
                                        &tm->tm_sec, fsec);
                                tmask |= DTK_TIME_M;
                            }
                            break;

                        case DTK_TIME:
                            /* previous field was "t" for ISO time */
                            dterr = DecodeNumberField(strlen(field[i]), field[i],
                                                      (fmask | DTK_DATE_M),
                                                      &tmask, tm,
                                                      fsec, &is2digits);
                            if (dterr < 0)
                                return dterr;
                            ftype[i] = dterr;

                            if (tmask != DTK_TIME_M)
                                return DTERR_BAD_FORMAT;
                            break;

                        default:
                            return DTERR_BAD_FORMAT;
                            break;
                    }

                    ptype = 0;
                    *dtype = DTK_DATE;
                }
                else
                {
                    char       *cp;
                    int            flen;

                    flen = strlen(field[i]);
                    cp = strchr(field[i], '.');

                    /* Embedded decimal? */
                    if (cp != NULL)
                    {
                        /*
                         * Under limited circumstances, we will accept a
                         * date...
                         */
                        if (i == 0 && nf >= 2 && ftype[nf - 1] == DTK_DATE)
                        {
                            dterr = DecodeDate(field[i], fmask,
                                               &tmask, &is2digits, tm);
                            if (dterr)
                                return dterr;
                        }
                        /* embedded decimal and several digits before? */
                        else if (flen - strlen(cp) > 2)
                        {
                            /*
                             * Interpret as a concatenated date or time Set
                             * the type field to allow decoding other fields
                             * later. Example: 20011223 or 040506
                             */
                            dterr = DecodeNumberField(flen, field[i],
                                                      (fmask | DTK_DATE_M),
                                                      &tmask, tm,
                                                      fsec, &is2digits);
                            if (dterr < 0)
                                return dterr;
                            ftype[i] = dterr;
                        }
                        else
                            return DTERR_BAD_FORMAT;
                    }
                    else if (flen > 4)
                    {
                        dterr = DecodeNumberField(flen, field[i],
                                                  (fmask | DTK_DATE_M),
                                                  &tmask, tm,
                                                  fsec, &is2digits);
                        if (dterr < 0)
                            return dterr;
                        ftype[i] = dterr;
                    }
                    /* otherwise it is a single date/time field... */
                    else
                    {
                        dterr = DecodeNumber(flen, field[i],
                                             FALSE,
                                             (fmask | DTK_DATE_M),
                                             &tmask, tm,
                                             fsec, &is2digits);
                        if (dterr)
                            return dterr;
                    }
                }
                break;

            case DTK_STRING:
            case DTK_SPECIAL:
                /* timezone abbrevs take precedence over built-in tokens */
                type = DecodeTimezoneAbbrev(i, field[i], &val, &valtz);
                if (type == UNKNOWN_FIELD)
                    type = DecodeSpecial(i, field[i], &val);
                if (type == IGNORE_DTF)
                    continue;

                tmask = DTK_M(type);
                switch (type)
                {
                    case RESERV:
                        switch (val)
                        {
                            case DTK_CURRENT:
                                ereport(ERROR,
                                        (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                                         errmsg("date/time value \"current\" is no longer supported")));
                                return DTERR_BAD_FORMAT;
                                break;

                            case DTK_NOW:
                                tmask = DTK_TIME_M;
                                *dtype = DTK_TIME;
                                GetCurrentTimeUsec(tm, fsec, NULL);
                                break;

                            case DTK_ZULU:
                                tmask = (DTK_TIME_M | DTK_M(TZ));
                                *dtype = DTK_TIME;
                                tm->tm_hour = 0;
                                tm->tm_min = 0;
                                tm->tm_sec = 0;
                                tm->tm_isdst = 0;
                                break;

                            default:
                                return DTERR_BAD_FORMAT;
                        }

                        break;

                    case DTZMOD:

                        /*
                         * daylight savings time modifier (solves "MET DST"
                         * syntax)
                         */
                        tmask |= DTK_M(DTZ);
                        tm->tm_isdst = 1;
                        if (tzp == NULL)
                            return DTERR_BAD_FORMAT;
                        *tzp -= val;
                        break;

                    case DTZ:

                        /*
                         * set mask for TZ here _or_ check for DTZ later when
                         * getting default timezone
                         */
                        tmask |= DTK_M(TZ);
                        tm->tm_isdst = 1;
                        if (tzp == NULL)
                            return DTERR_BAD_FORMAT;
                        *tzp = -val;
                        ftype[i] = DTK_TZ;
                        break;

                    case TZ:
                        tm->tm_isdst = 0;
                        if (tzp == NULL)
                            return DTERR_BAD_FORMAT;
                        *tzp = -val;
                        ftype[i] = DTK_TZ;
                        break;

                    case DYNTZ:
                        tmask |= DTK_M(TZ);
                        if (tzp == NULL)
                            return DTERR_BAD_FORMAT;
                        /* we'll determine the actual offset later */
                        abbrevTz = valtz;
                        abbrev = field[i];
                        ftype[i] = DTK_TZ;
                        break;

                    case AMPM:
                        mer = val;
                        break;

                    case ADBC:
                        bc = (val == BC);
                        break;

                    case UNITS:
                        tmask = 0;
                        ptype = val;
                        break;

                    case ISOTIME:
                        tmask = 0;

                        /***
                         * We will need one of the following fields:
                         *    DTK_NUMBER should be hhmmss.fff
                         *    DTK_TIME should be hh:mm:ss.fff
                         *    DTK_DATE should be hhmmss-zz
                         ***/
                        if (i >= nf - 1 ||
                            (ftype[i + 1] != DTK_NUMBER &&
                             ftype[i + 1] != DTK_TIME &&
                             ftype[i + 1] != DTK_DATE))
                            return DTERR_BAD_FORMAT;

                        ptype = val;
                        break;

                    case UNKNOWN_FIELD:

                        /*
                         * Before giving up and declaring error, check to see
                         * if it is an all-alpha timezone name.
                         */
                        namedTz = pg_tzset(field[i]);
                        if (!namedTz)
                            return DTERR_BAD_FORMAT;
                        /* we'll apply the zone setting below */
                        tmask = DTK_M(TZ);
                        break;

                    default:
                        return DTERR_BAD_FORMAT;
                }
                break;

            default:
                return DTERR_BAD_FORMAT;
        }

        if (tmask & fmask)
            return DTERR_BAD_FORMAT;
        fmask |= tmask;
    }                            /* end loop over fields */

    /* do final checking/adjustment of Y/M/D fields */
    dterr = ValidateDate(fmask, isjulian, is2digits, bc, tm);
    if (dterr)
        return dterr;

    /* handle AM/PM */
    if (mer != HR24 && tm->tm_hour > HOURS_PER_DAY / 2)
        return DTERR_FIELD_OVERFLOW;
    if (mer == AM && tm->tm_hour == HOURS_PER_DAY / 2)
        tm->tm_hour = 0;
    else if (mer == PM && tm->tm_hour != HOURS_PER_DAY / 2)
        tm->tm_hour += HOURS_PER_DAY / 2;

    /*
     * This should match the checks in make_timestamp_internal
     */
    if (tm->tm_hour < 0 || tm->tm_min < 0 || tm->tm_min > MINS_PER_HOUR - 1 ||
        tm->tm_sec < 0 || tm->tm_sec > SECS_PER_MINUTE ||
        tm->tm_hour > HOURS_PER_DAY ||
    /* test for > 24:00:00 */
        (tm->tm_hour == HOURS_PER_DAY &&
         (tm->tm_min > 0 || tm->tm_sec > 0 || *fsec > 0)) ||
        *fsec < INT64CONST(0) || *fsec > USECS_PER_SEC)
        return DTERR_FIELD_OVERFLOW;

    if ((fmask & DTK_TIME_M) != DTK_TIME_M)
        return DTERR_BAD_FORMAT;

    /*
     * If we had a full timezone spec, compute the offset (we could not do it
     * before, because we may need the date to resolve DST status).
     */
    if (namedTz != NULL)
    {
        long int    gmtoff;

        /* daylight savings time modifier disallowed with full TZ */
        if (fmask & DTK_M(DTZMOD))
            return DTERR_BAD_FORMAT;

        /* if non-DST zone, we do not need to know the date */
        if (pg_get_timezone_offset(namedTz, &gmtoff))
        {
            *tzp = -(int) gmtoff;
        }
        else
        {
            /* a date has to be specified */
            if ((fmask & DTK_DATE_M) != DTK_DATE_M)
                return DTERR_BAD_FORMAT;
            *tzp = DetermineTimeZoneOffset(tm, namedTz);
        }
    }

    /*
     * Likewise, if we had a dynamic timezone abbreviation, resolve it now.
     */
    if (abbrevTz != NULL)
    {
        struct pg_tm tt,
                   *tmp = &tt;

        /*
         * daylight savings time modifier but no standard timezone? then error
         */
        if (fmask & DTK_M(DTZMOD))
            return DTERR_BAD_FORMAT;

        if ((fmask & DTK_DATE_M) == 0)
            GetCurrentDateTime(tmp);
        else
        {
            tmp->tm_year = tm->tm_year;
            tmp->tm_mon = tm->tm_mon;
            tmp->tm_mday = tm->tm_mday;
        }
        tmp->tm_hour = tm->tm_hour;
        tmp->tm_min = tm->tm_min;
        tmp->tm_sec = tm->tm_sec;
        *tzp = DetermineTimeZoneAbbrevOffset(tmp, abbrev, abbrevTz);
        tm->tm_isdst = tmp->tm_isdst;
    }

    /* timezone not specified? then use session timezone */
    if (tzp != NULL && !(fmask & DTK_M(TZ)))
    {
        struct pg_tm tt,
                   *tmp = &tt;

        /*
         * daylight savings time modifier but no standard timezone? then error
         */
        if (fmask & DTK_M(DTZMOD))
            return DTERR_BAD_FORMAT;

        if ((fmask & DTK_DATE_M) == 0)
            GetCurrentDateTime(tmp);
        else
        {
            tmp->tm_year = tm->tm_year;
            tmp->tm_mon = tm->tm_mon;
            tmp->tm_mday = tm->tm_mday;
        }
        tmp->tm_hour = tm->tm_hour;
        tmp->tm_min = tm->tm_min;
        tmp->tm_sec = tm->tm_sec;
        *tzp = DetermineTimeZoneOffset(tmp, session_timezone);
        tm->tm_isdst = tmp->tm_isdst;
    }

    return 0;
}

/* DecodeDate()
 * Decode date string which includes delimiters.
 * Return 0 if okay, a DTERR code if not.
 *
 *    str: field to be parsed
 *    fmask: bitmask for field types already seen
 *    *tmask: receives bitmask for fields found here
 *    *is2digits: set to TRUE if we find 2-digit year
 *    *tm: field values are stored into appropriate members of this struct
 */
static int
DecodeDate(char *str, int fmask, int *tmask, bool *is2digits,
           struct pg_tm *tm)
{// #lizard forgives
    fsec_t        fsec;
    int            nf = 0;
    int            i,
                len;
    int            dterr;
    bool        haveTextMonth = FALSE;
    int            type,
                val,
                dmask = 0;
    char       *field[MAXDATEFIELDS];

    *tmask = 0;

    /* parse this string... */
    while (*str != '\0' && nf < MAXDATEFIELDS)
    {
        /* skip field separators */
        while (*str != '\0' && !isalnum((unsigned char) *str))
            str++;

        if (*str == '\0')
            return DTERR_BAD_FORMAT;    /* end of string after separator */

        field[nf] = str;
        if (isdigit((unsigned char) *str))
        {
            while (isdigit((unsigned char) *str))
                str++;
        }
        else if (isalpha((unsigned char) *str))
        {
            while (isalpha((unsigned char) *str))
                str++;
        }

        /* Just get rid of any non-digit, non-alpha characters... */
        if (*str != '\0')
            *str++ = '\0';
        nf++;
    }

    /* look first for text fields, since that will be unambiguous month */
    for (i = 0; i < nf; i++)
    {
        if (isalpha((unsigned char) *field[i]))
        {
            type = DecodeSpecial(i, field[i], &val);
            if (type == IGNORE_DTF)
                continue;

            dmask = DTK_M(type);
            switch (type)
            {
                case MONTH:
                    tm->tm_mon = val;
                    haveTextMonth = TRUE;
                    break;

                default:
                    return DTERR_BAD_FORMAT;
            }
            if (fmask & dmask)
                return DTERR_BAD_FORMAT;

            fmask |= dmask;
            *tmask |= dmask;

            /* mark this field as being completed */
            field[i] = NULL;
        }
    }

    /* now pick up remaining numeric fields */
    for (i = 0; i < nf; i++)
    {
        if (field[i] == NULL)
            continue;

        if ((len = strlen(field[i])) <= 0)
            return DTERR_BAD_FORMAT;

        dterr = DecodeNumber(len, field[i], haveTextMonth, fmask,
                             &dmask, tm,
                             &fsec, is2digits);
        if (dterr)
            return dterr;

        if (fmask & dmask)
            return DTERR_BAD_FORMAT;

        fmask |= dmask;
        *tmask |= dmask;
    }

    if ((fmask & ~(DTK_M(DOY) | DTK_M(TZ))) != DTK_DATE_M)
        return DTERR_BAD_FORMAT;

    /* validation of the field values must wait until ValidateDate() */

    return 0;
}

/* ValidateDate()
 * Check valid year/month/day values, handle BC and DOY cases
 * Return 0 if okay, a DTERR code if not.
 */
int
ValidateDate(int fmask, bool isjulian, bool is2digits, bool bc,
             struct pg_tm *tm)
{// #lizard forgives
    if (fmask & DTK_M(YEAR))
    {
        if (isjulian)
        {
            /* tm_year is correct and should not be touched */
        }
        else if (bc)
        {
            /* there is no year zero in AD/BC notation */
            if (tm->tm_year <= 0)
                return DTERR_FIELD_OVERFLOW;
            /* internally, we represent 1 BC as year zero, 2 BC as -1, etc */
            tm->tm_year = -(tm->tm_year - 1);
        }
        else if (is2digits)
        {
            /* process 1 or 2-digit input as 1970-2069 AD, allow '0' and '00' */
            if (tm->tm_year < 0)    /* just paranoia */
                return DTERR_FIELD_OVERFLOW;
            if (tm->tm_year < 70)
                tm->tm_year += 2000;
            else if (tm->tm_year < 100)
                tm->tm_year += 1900;
        }
        else
        {
            /* there is no year zero in AD/BC notation */
            if (tm->tm_year <= 0)
                return DTERR_FIELD_OVERFLOW;
        }
    }

    /* now that we have correct year, decode DOY */
    if (fmask & DTK_M(DOY))
    {
        j2date(date2j(tm->tm_year, 1, 1) + tm->tm_yday - 1,
               &tm->tm_year, &tm->tm_mon, &tm->tm_mday);
    }

    /* check for valid month */
    if (fmask & DTK_M(MONTH))
    {
        if (tm->tm_mon < 1 || tm->tm_mon > MONTHS_PER_YEAR)
            return DTERR_MD_FIELD_OVERFLOW;
    }

    /* minimal check for valid day */
    if (fmask & DTK_M(DAY))
    {
        if (tm->tm_mday < 1 || tm->tm_mday > 31)
            return DTERR_MD_FIELD_OVERFLOW;
    }

    if ((fmask & DTK_DATE_M) == DTK_DATE_M)
    {
        /*
         * Check for valid day of month, now that we know for sure the month
         * and year.  Note we don't use MD_FIELD_OVERFLOW here, since it seems
         * unlikely that "Feb 29" is a YMD-order error.
         */
        if (tm->tm_mday > day_tab[isleap(tm->tm_year)][tm->tm_mon - 1])
            return DTERR_FIELD_OVERFLOW;
    }

    return 0;
}


/* DecodeTime()
 * Decode time string which includes delimiters.
 * Return 0 if okay, a DTERR code if not.
 *
 * Only check the lower limit on hours, since this same code can be
 * used to represent time spans.
 */
static int
DecodeTime(char *str, int fmask, int range,
           int *tmask, struct pg_tm *tm, fsec_t *fsec)
{// #lizard forgives
    char       *cp;
    int            dterr;

    *tmask = DTK_TIME_M;

    errno = 0;
    tm->tm_hour = strtoint(str, &cp, 10);
    if (errno == ERANGE)
        return DTERR_FIELD_OVERFLOW;
    if (*cp != ':')
        return DTERR_BAD_FORMAT;
    errno = 0;
    tm->tm_min = strtoint(cp + 1, &cp, 10);
    if (errno == ERANGE)
        return DTERR_FIELD_OVERFLOW;
    if (*cp == '\0')
    {
        tm->tm_sec = 0;
        *fsec = 0;
        /* If it's a MINUTE TO SECOND interval, take 2 fields as being mm:ss */
        if (range == (INTERVAL_MASK(MINUTE) | INTERVAL_MASK(SECOND)))
        {
            tm->tm_sec = tm->tm_min;
            tm->tm_min = tm->tm_hour;
            tm->tm_hour = 0;
        }
    }
    else if (*cp == '.')
    {
        /* always assume mm:ss.sss is MINUTE TO SECOND */
        dterr = ParseFractionalSecond(cp, fsec);
        if (dterr)
            return dterr;
        tm->tm_sec = tm->tm_min;
        tm->tm_min = tm->tm_hour;
        tm->tm_hour = 0;
    }
    else if (*cp == ':')
    {
        errno = 0;
        tm->tm_sec = strtoint(cp + 1, &cp, 10);
        if (errno == ERANGE)
            return DTERR_FIELD_OVERFLOW;
        if (*cp == '\0')
            *fsec = 0;
        else if (*cp == '.')
        {
            dterr = ParseFractionalSecond(cp, fsec);
            if (dterr)
                return dterr;
        }
        else
            return DTERR_BAD_FORMAT;
    }
    else
        return DTERR_BAD_FORMAT;

    /* do a sanity check */
    if (tm->tm_hour < 0 || tm->tm_min < 0 || tm->tm_min > MINS_PER_HOUR - 1 ||
        tm->tm_sec < 0 || tm->tm_sec > SECS_PER_MINUTE ||
        *fsec < INT64CONST(0) ||
        *fsec > USECS_PER_SEC)
        return DTERR_FIELD_OVERFLOW;

    return 0;
}


/* DecodeNumber()
 * Interpret plain numeric field as a date value in context.
 * Return 0 if okay, a DTERR code if not.
 */
static int
DecodeNumber(int flen, char *str, bool haveTextMonth, int fmask,
             int *tmask, struct pg_tm *tm, fsec_t *fsec, bool *is2digits)
{// #lizard forgives
    int            val;
    char       *cp;
    int            dterr;

    *tmask = 0;

    errno = 0;
    val = strtoint(str, &cp, 10);
    if (errno == ERANGE)
        return DTERR_FIELD_OVERFLOW;
    if (cp == str)
        return DTERR_BAD_FORMAT;

    if (*cp == '.')
    {
        /*
         * More than two digits before decimal point? Then could be a date or
         * a run-together time: 2001.360 20011225 040506.789
         */
        if (cp - str > 2)
        {
            dterr = DecodeNumberField(flen, str,
                                      (fmask | DTK_DATE_M),
                                      tmask, tm,
                                      fsec, is2digits);
            if (dterr < 0)
                return dterr;
            return 0;
        }

        dterr = ParseFractionalSecond(cp, fsec);
        if (dterr)
            return dterr;
    }
    else if (*cp != '\0')
        return DTERR_BAD_FORMAT;

    /* Special case for day of year */
    if (flen == 3 && (fmask & DTK_DATE_M) == DTK_M(YEAR) && val >= 1 &&
        val <= 366)
    {
        *tmask = (DTK_M(DOY) | DTK_M(MONTH) | DTK_M(DAY));
        tm->tm_yday = val;
        /* tm_mon and tm_mday can't actually be set yet ... */
        return 0;
    }

    /* Switch based on what we have so far */
    switch (fmask & DTK_DATE_M)
    {
        case 0:

            /*
             * Nothing so far; make a decision about what we think the input
             * is.  There used to be lots of heuristics here, but the
             * consensus now is to be paranoid.  It *must* be either
             * YYYY-MM-DD (with a more-than-two-digit year field), or the
             * field order defined by DateOrder.
             */
            if (flen >= 3 || DateOrder == DATEORDER_YMD)
            {
                *tmask = DTK_M(YEAR);
                tm->tm_year = val;
            }
            else if (DateOrder == DATEORDER_DMY)
            {
                *tmask = DTK_M(DAY);
                tm->tm_mday = val;
            }
            else
            {
                *tmask = DTK_M(MONTH);
                tm->tm_mon = val;
            }
            break;

        case (DTK_M(YEAR)):
            /* Must be at second field of YY-MM-DD */
            *tmask = DTK_M(MONTH);
            tm->tm_mon = val;
            break;

        case (DTK_M(MONTH)):
            if (haveTextMonth)
            {
                /*
                 * We are at the first numeric field of a date that included a
                 * textual month name.  We want to support the variants
                 * MON-DD-YYYY, DD-MON-YYYY, and YYYY-MON-DD as unambiguous
                 * inputs.  We will also accept MON-DD-YY or DD-MON-YY in
                 * either DMY or MDY modes, as well as YY-MON-DD in YMD mode.
                 */
                if (flen >= 3 || DateOrder == DATEORDER_YMD)
                {
                    *tmask = DTK_M(YEAR);
                    tm->tm_year = val;
                }
                else
                {
                    *tmask = DTK_M(DAY);
                    tm->tm_mday = val;
                }
            }
            else
            {
                /* Must be at second field of MM-DD-YY */
                *tmask = DTK_M(DAY);
                tm->tm_mday = val;
            }
            break;

        case (DTK_M(YEAR) | DTK_M(MONTH)):
            if (haveTextMonth)
            {
                /* Need to accept DD-MON-YYYY even in YMD mode */
                if (flen >= 3 && *is2digits)
                {
                    /* Guess that first numeric field is day was wrong */
                    *tmask = DTK_M(DAY);    /* YEAR is already set */
                    tm->tm_mday = tm->tm_year;
                    tm->tm_year = val;
                    *is2digits = FALSE;
                }
                else
                {
                    *tmask = DTK_M(DAY);
                    tm->tm_mday = val;
                }
            }
            else
            {
                /* Must be at third field of YY-MM-DD */
                *tmask = DTK_M(DAY);
                tm->tm_mday = val;
            }
            break;

        case (DTK_M(DAY)):
            /* Must be at second field of DD-MM-YY */
            *tmask = DTK_M(MONTH);
            tm->tm_mon = val;
            break;

        case (DTK_M(MONTH) | DTK_M(DAY)):
            /* Must be at third field of DD-MM-YY or MM-DD-YY */
            *tmask = DTK_M(YEAR);
            tm->tm_year = val;
            break;

        case (DTK_M(YEAR) | DTK_M(MONTH) | DTK_M(DAY)):
            /* we have all the date, so it must be a time field */
            dterr = DecodeNumberField(flen, str, fmask,
                                      tmask, tm,
                                      fsec, is2digits);
            if (dterr < 0)
                return dterr;
            return 0;

        default:
            /* Anything else is bogus input */
            return DTERR_BAD_FORMAT;
    }

    /*
     * When processing a year field, mark it for adjustment if it's only one
     * or two digits.
     */
    if (*tmask == DTK_M(YEAR))
        *is2digits = (flen <= 2);

    return 0;
}


/* DecodeNumberField()
 * Interpret numeric string as a concatenated date or time field.
 * Return a DTK token (>= 0) if successful, a DTERR code (< 0) if not.
 *
 * Use the context of previously decoded fields to help with
 * the interpretation.
 */
static int
DecodeNumberField(int len, char *str, int fmask,
                  int *tmask, struct pg_tm *tm, fsec_t *fsec, bool *is2digits)
{// #lizard forgives
    char       *cp;

    /*
     * Have a decimal point? Then this is a date or something with a seconds
     * field...
     */
    if ((cp = strchr(str, '.')) != NULL)
    {
        /*
         * Can we use ParseFractionalSecond here?  Not clear whether trailing
         * junk should be rejected ...
         */
        double        frac;

        errno = 0;
        frac = strtod(cp, NULL);
        if (errno != 0)
            return DTERR_BAD_FORMAT;
        *fsec = rint(frac * 1000000);
        /* Now truncate off the fraction for further processing */
        *cp = '\0';
        len = strlen(str);
    }
    /* No decimal point and no complete date yet? */
    else if ((fmask & DTK_DATE_M) != DTK_DATE_M)
    {
        if (len >= 6)
        {
            *tmask = DTK_DATE_M;

            /*
             * Start from end and consider first 2 as Day, next 2 as Month,
             * and the rest as Year.
             */
            tm->tm_mday = atoi(str + (len - 2));
            *(str + (len - 2)) = '\0';
            tm->tm_mon = atoi(str + (len - 4));
            *(str + (len - 4)) = '\0';
            tm->tm_year = atoi(str);
            if ((len - 4) == 2)
                *is2digits = TRUE;

            return DTK_DATE;
        }
    }

    /* not all time fields are specified? */
    if ((fmask & DTK_TIME_M) != DTK_TIME_M)
    {
        /* hhmmss */
        if (len == 6)
        {
            *tmask = DTK_TIME_M;
            tm->tm_sec = atoi(str + 4);
            *(str + 4) = '\0';
            tm->tm_min = atoi(str + 2);
            *(str + 2) = '\0';
            tm->tm_hour = atoi(str);

            return DTK_TIME;
        }
        /* hhmm? */
        else if (len == 4)
        {
            *tmask = DTK_TIME_M;
            tm->tm_sec = 0;
            tm->tm_min = atoi(str + 2);
            *(str + 2) = '\0';
            tm->tm_hour = atoi(str);

            return DTK_TIME;
        }
    }

    return DTERR_BAD_FORMAT;
}


/* DecodeTimezone()
 * Interpret string as a numeric timezone.
 *
 * Return 0 if okay (and set *tzp), a DTERR code if not okay.
 */
int
DecodeTimezone(char *str, int *tzp)
{// #lizard forgives
    int            tz;
    int            hr,
                min,
                sec = 0;
    char       *cp;

    /* leading character must be "+" or "-" */
    if (*str != '+' && *str != '-')
        return DTERR_BAD_FORMAT;

    errno = 0;
    hr = strtoint(str + 1, &cp, 10);
    if (errno == ERANGE)
        return DTERR_TZDISP_OVERFLOW;

    /* explicit delimiter? */
    if (*cp == ':')
    {
        errno = 0;
        min = strtoint(cp + 1, &cp, 10);
        if (errno == ERANGE)
            return DTERR_TZDISP_OVERFLOW;
        if (*cp == ':')
        {
            errno = 0;
            sec = strtoint(cp + 1, &cp, 10);
            if (errno == ERANGE)
                return DTERR_TZDISP_OVERFLOW;
        }
    }
    /* otherwise, might have run things together... */
    else if (*cp == '\0' && strlen(str) > 3)
    {
        min = hr % 100;
        hr = hr / 100;
        /* we could, but don't, support a run-together hhmmss format */
    }
    else
        min = 0;

    /* Range-check the values; see notes in datatype/timestamp.h */
    if (hr < 0 || hr > MAX_TZDISP_HOUR)
        return DTERR_TZDISP_OVERFLOW;
    if (min < 0 || min >= MINS_PER_HOUR)
        return DTERR_TZDISP_OVERFLOW;
    if (sec < 0 || sec >= SECS_PER_MINUTE)
        return DTERR_TZDISP_OVERFLOW;

    tz = (hr * MINS_PER_HOUR + min) * SECS_PER_MINUTE + sec;
    if (*str == '-')
        tz = -tz;

    *tzp = -tz;

    if (*cp != '\0')
        return DTERR_BAD_FORMAT;

    return 0;
}


/* DecodeTimezoneAbbrev()
 * Interpret string as a timezone abbreviation, if possible.
 *
 * Returns an abbreviation type (TZ, DTZ, or DYNTZ), or UNKNOWN_FIELD if
 * string is not any known abbreviation.  On success, set *offset and *tz to
 * represent the UTC offset (for TZ or DTZ) or underlying zone (for DYNTZ).
 * Note that full timezone names (such as America/New_York) are not handled
 * here, mostly for historical reasons.
 *
 * Given string must be lowercased already.
 *
 * Implement a cache lookup since it is likely that dates
 *    will be related in format.
 */
int
DecodeTimezoneAbbrev(int field, char *lowtoken,
                     int *offset, pg_tz **tz)
{
    int            type;
    const datetkn *tp;

    tp = abbrevcache[field];
    /* use strncmp so that we match truncated tokens */
    if (tp == NULL || strncmp(lowtoken, tp->token, TOKMAXLEN) != 0)
    {
        if (zoneabbrevtbl)
            tp = datebsearch(lowtoken, zoneabbrevtbl->abbrevs,
                             zoneabbrevtbl->numabbrevs);
        else
            tp = NULL;
    }
    if (tp == NULL)
    {
        type = UNKNOWN_FIELD;
        *offset = 0;
        *tz = NULL;
    }
    else
    {
        abbrevcache[field] = tp;
        type = tp->type;
        if (type == DYNTZ)
        {
            *offset = 0;
            *tz = FetchDynamicTimeZone(zoneabbrevtbl, tp);
        }
        else
        {
            *offset = tp->value;
            *tz = NULL;
        }
    }

    return type;
}


/* DecodeSpecial()
 * Decode text string using lookup table.
 *
 * Recognizes the keywords listed in datetktbl.
 * Note: at one time this would also recognize timezone abbreviations,
 * but no more; use DecodeTimezoneAbbrev for that.
 *
 * Given string must be lowercased already.
 *
 * Implement a cache lookup since it is likely that dates
 *    will be related in format.
 */
int
DecodeSpecial(int field, char *lowtoken, int *val)
{
    int            type;
    const datetkn *tp;

    tp = datecache[field];
    /* use strncmp so that we match truncated tokens */
    if (tp == NULL || strncmp(lowtoken, tp->token, TOKMAXLEN) != 0)
    {
        tp = datebsearch(lowtoken, datetktbl, szdatetktbl);
    }
    if (tp == NULL)
    {
        type = UNKNOWN_FIELD;
        *val = 0;
    }
    else
    {
        datecache[field] = tp;
        type = tp->type;
        *val = tp->value;
    }

    return type;
}


/* ClearPgTM
 *
 * Zero out a pg_tm and associated fsec_t
 */
static inline void
ClearPgTm(struct pg_tm *tm, fsec_t *fsec)
{
    tm->tm_year = 0;
    tm->tm_mon = 0;
    tm->tm_mday = 0;
    tm->tm_hour = 0;
    tm->tm_min = 0;
    tm->tm_sec = 0;
    *fsec = 0;
}


/* DecodeInterval()
 * Interpret previously parsed fields for general time interval.
 * Returns 0 if successful, DTERR code if bogus input detected.
 * dtype, tm, fsec are output parameters.
 *
 * Allow "date" field DTK_DATE since this could be just
 *    an unsigned floating point number. - thomas 1997-11-16
 *
 * Allow ISO-style time span, with implicit units on number of days
 *    preceding an hh:mm:ss field. - thomas 1998-04-30
 */
int
DecodeInterval(char **field, int *ftype, int nf, int range,
               int *dtype, struct pg_tm *tm, fsec_t *fsec)
{// #lizard forgives
    bool        is_before = FALSE;
    char       *cp;
    int            fmask = 0,
                tmask,
                type;
    int            i;
    int            dterr;
    int            val;
    double        fval;

    *dtype = DTK_DELTA;
    type = IGNORE_DTF;
    ClearPgTm(tm, fsec);

    /* read through list backwards to pick up units before values */
    for (i = nf - 1; i >= 0; i--)
    {
        switch (ftype[i])
        {
            case DTK_TIME:
                dterr = DecodeTime(field[i], fmask, range,
                                   &tmask, tm, fsec);
                if (dterr)
                    return dterr;
                type = DTK_DAY;
                break;

            case DTK_TZ:

                /*
                 * Timezone means a token with a leading sign character and at
                 * least one digit; there could be ':', '.', '-' embedded in
                 * it as well.
                 */
                Assert(*field[i] == '-' || *field[i] == '+');

                /*
                 * Check for signed hh:mm or hh:mm:ss.  If so, process exactly
                 * like DTK_TIME case above, plus handling the sign.
                 */
                if (strchr(field[i] + 1, ':') != NULL &&
                    DecodeTime(field[i] + 1, fmask, range,
                               &tmask, tm, fsec) == 0)
                {
                    if (*field[i] == '-')
                    {
                        /* flip the sign on all fields */
                        tm->tm_hour = -tm->tm_hour;
                        tm->tm_min = -tm->tm_min;
                        tm->tm_sec = -tm->tm_sec;
                        *fsec = -(*fsec);
                    }

                    /*
                     * Set the next type to be a day, if units are not
                     * specified. This handles the case of '1 +02:03' since we
                     * are reading right to left.
                     */
                    type = DTK_DAY;
                    break;
                }

                /*
                 * Otherwise, fall through to DTK_NUMBER case, which can
                 * handle signed float numbers and signed year-month values.
                 */

                /* FALL THROUGH */

            case DTK_DATE:
            case DTK_NUMBER:
                if (type == IGNORE_DTF)
                {
                    /* use typmod to decide what rightmost field is */
                    switch (range)
                    {
                        case INTERVAL_MASK(YEAR):
                            type = DTK_YEAR;
                            break;
                        case INTERVAL_MASK(MONTH):
                        case INTERVAL_MASK(YEAR) | INTERVAL_MASK(MONTH):
                            type = DTK_MONTH;
                            break;
                        case INTERVAL_MASK(DAY):
                            type = DTK_DAY;
                            break;
                        case INTERVAL_MASK(HOUR):
                        case INTERVAL_MASK(DAY) | INTERVAL_MASK(HOUR):
                            type = DTK_HOUR;
                            break;
                        case INTERVAL_MASK(MINUTE):
                        case INTERVAL_MASK(HOUR) | INTERVAL_MASK(MINUTE):
                        case INTERVAL_MASK(DAY) | INTERVAL_MASK(HOUR) | INTERVAL_MASK(MINUTE):
                            type = DTK_MINUTE;
                            break;
                        case INTERVAL_MASK(SECOND):
                        case INTERVAL_MASK(MINUTE) | INTERVAL_MASK(SECOND):
                        case INTERVAL_MASK(HOUR) | INTERVAL_MASK(MINUTE) | INTERVAL_MASK(SECOND):
                        case INTERVAL_MASK(DAY) | INTERVAL_MASK(HOUR) | INTERVAL_MASK(MINUTE) | INTERVAL_MASK(SECOND):
                            type = DTK_SECOND;
                            break;
                        default:
                            type = DTK_SECOND;
                            break;
                    }
                }

                errno = 0;
                val = strtoint(field[i], &cp, 10);
                if (errno == ERANGE)
                    return DTERR_FIELD_OVERFLOW;

                if (*cp == '-')
                {
                    /* SQL "years-months" syntax */
                    int            val2;

                    val2 = strtoint(cp + 1, &cp, 10);
                    if (errno == ERANGE || val2 < 0 || val2 >= MONTHS_PER_YEAR)
                        return DTERR_FIELD_OVERFLOW;
                    if (*cp != '\0')
                        return DTERR_BAD_FORMAT;
                    type = DTK_MONTH;
                    if (*field[i] == '-')
                        val2 = -val2;
                    if (((double) val * MONTHS_PER_YEAR + val2) > INT_MAX ||
                        ((double) val * MONTHS_PER_YEAR + val2) < INT_MIN)
                        return DTERR_FIELD_OVERFLOW;
                    val = val * MONTHS_PER_YEAR + val2;
                    fval = 0;
                }
                else if (*cp == '.')
                {
                    errno = 0;
                    fval = strtod(cp, &cp);
                    if (*cp != '\0' || errno != 0)
                        return DTERR_BAD_FORMAT;

                    if (*field[i] == '-')
                        fval = -fval;
                }
                else if (*cp == '\0')
                    fval = 0;
                else
                    return DTERR_BAD_FORMAT;

                tmask = 0;        /* DTK_M(type); */

                switch (type)
                {
                    case DTK_MICROSEC:
                        *fsec += rint(val + fval);
                        tmask = DTK_M(MICROSECOND);
                        break;

                    case DTK_MILLISEC:
                        /* avoid overflowing the fsec field */
                        tm->tm_sec += val / 1000;
                        val -= (val / 1000) * 1000;
                        *fsec += rint((val + fval) * 1000);
                        tmask = DTK_M(MILLISECOND);
                        break;

                    case DTK_SECOND:
                        tm->tm_sec += val;
                        *fsec += rint(fval * 1000000);

                        /*
                         * If any subseconds were specified, consider this
                         * microsecond and millisecond input as well.
                         */
                        if (fval == 0)
                            tmask = DTK_M(SECOND);
                        else
                            tmask = DTK_ALL_SECS_M;
                        break;

                    case DTK_MINUTE:
                        tm->tm_min += val;
                        AdjustFractSeconds(fval, tm, fsec, SECS_PER_MINUTE);
                        tmask = DTK_M(MINUTE);
                        break;

                    case DTK_HOUR:
                        tm->tm_hour += val;
                        AdjustFractSeconds(fval, tm, fsec, SECS_PER_HOUR);
                        tmask = DTK_M(HOUR);
                        type = DTK_DAY; /* set for next field */
                        break;

                    case DTK_DAY:
                        tm->tm_mday += val;
                        AdjustFractSeconds(fval, tm, fsec, SECS_PER_DAY);
                        tmask = DTK_M(DAY);
                        break;

                    case DTK_WEEK:
                        tm->tm_mday += val * 7;
                        AdjustFractDays(fval, tm, fsec, 7);
                        tmask = DTK_M(WEEK);
                        break;

                    case DTK_MONTH:
                        tm->tm_mon += val;
                        AdjustFractDays(fval, tm, fsec, DAYS_PER_MONTH);
                        tmask = DTK_M(MONTH);
                        break;

                    case DTK_YEAR:
                        tm->tm_year += val;
                        if (fval != 0)
                            tm->tm_mon += fval * MONTHS_PER_YEAR;
                        tmask = DTK_M(YEAR);
                        break;

                    case DTK_DECADE:
                        tm->tm_year += val * 10;
                        if (fval != 0)
                            tm->tm_mon += fval * MONTHS_PER_YEAR * 10;
                        tmask = DTK_M(DECADE);
                        break;

                    case DTK_CENTURY:
                        tm->tm_year += val * 100;
                        if (fval != 0)
                            tm->tm_mon += fval * MONTHS_PER_YEAR * 100;
                        tmask = DTK_M(CENTURY);
                        break;

                    case DTK_MILLENNIUM:
                        tm->tm_year += val * 1000;
                        if (fval != 0)
                            tm->tm_mon += fval * MONTHS_PER_YEAR * 1000;
                        tmask = DTK_M(MILLENNIUM);
                        break;

                    default:
                        return DTERR_BAD_FORMAT;
                }
                break;

            case DTK_STRING:
            case DTK_SPECIAL:
                type = DecodeUnits(i, field[i], &val);
                if (type == IGNORE_DTF)
                    continue;

                tmask = 0;        /* DTK_M(type); */
                switch (type)
                {
                    case UNITS:
                        type = val;
                        break;

                    case AGO:
                        is_before = TRUE;
                        type = val;
                        break;

                    case RESERV:
                        tmask = (DTK_DATE_M | DTK_TIME_M);
                        *dtype = val;
                        break;

                    default:
                        return DTERR_BAD_FORMAT;
                }
                break;

            default:
                return DTERR_BAD_FORMAT;
        }

        if (tmask & fmask)
            return DTERR_BAD_FORMAT;
        fmask |= tmask;
    }

    /* ensure that at least one time field has been found */
    if (fmask == 0)
        return DTERR_BAD_FORMAT;

    /* ensure fractional seconds are fractional */
    if (*fsec != 0)
    {
        int            sec;

        sec = *fsec / USECS_PER_SEC;
        *fsec -= sec * USECS_PER_SEC;
        tm->tm_sec += sec;
    }

    /*----------
     * The SQL standard defines the interval literal
     *     '-1 1:00:00'
     * to mean "negative 1 days and negative 1 hours", while Postgres
     * traditionally treats this as meaning "negative 1 days and positive
     * 1 hours".  In SQL_STANDARD intervalstyle, we apply the leading sign
     * to all fields if there are no other explicit signs.
     *
     * We leave the signs alone if there are additional explicit signs.
     * This protects us against misinterpreting postgres-style dump output,
     * since the postgres-style output code has always put an explicit sign on
     * all fields following a negative field.  But note that SQL-spec output
     * is ambiguous and can be misinterpreted on load!    (So it's best practice
     * to dump in postgres style, not SQL style.)
     *----------
     */
    if (IntervalStyle == INTSTYLE_SQL_STANDARD && *field[0] == '-')
    {
        /* Check for additional explicit signs */
        bool        more_signs = false;

        for (i = 1; i < nf; i++)
        {
            if (*field[i] == '-' || *field[i] == '+')
            {
                more_signs = true;
                break;
            }
        }

        if (!more_signs)
        {
            /*
             * Rather than re-determining which field was field[0], just force
             * 'em all negative.
             */
            if (*fsec > 0)
                *fsec = -(*fsec);
            if (tm->tm_sec > 0)
                tm->tm_sec = -tm->tm_sec;
            if (tm->tm_min > 0)
                tm->tm_min = -tm->tm_min;
            if (tm->tm_hour > 0)
                tm->tm_hour = -tm->tm_hour;
            if (tm->tm_mday > 0)
                tm->tm_mday = -tm->tm_mday;
            if (tm->tm_mon > 0)
                tm->tm_mon = -tm->tm_mon;
            if (tm->tm_year > 0)
                tm->tm_year = -tm->tm_year;
        }
    }

    /* finally, AGO negates everything */
    if (is_before)
    {
        *fsec = -(*fsec);
        tm->tm_sec = -tm->tm_sec;
        tm->tm_min = -tm->tm_min;
        tm->tm_hour = -tm->tm_hour;
        tm->tm_mday = -tm->tm_mday;
        tm->tm_mon = -tm->tm_mon;
        tm->tm_year = -tm->tm_year;
    }

    return 0;
}


/*
 * Helper functions to avoid duplicated code in DecodeISO8601Interval.
 *
 * Parse a decimal value and break it into integer and fractional parts.
 * Returns 0 or DTERR code.
 */
static int
ParseISO8601Number(char *str, char **endptr, int *ipart, double *fpart)
{// #lizard forgives
    double        val;

    if (!(isdigit((unsigned char) *str) || *str == '-' || *str == '.'))
        return DTERR_BAD_FORMAT;
    errno = 0;
    val = strtod(str, endptr);
    /* did we not see anything that looks like a double? */
    if (*endptr == str || errno != 0)
        return DTERR_BAD_FORMAT;
    /* watch out for overflow */
    if (val < INT_MIN || val > INT_MAX)
        return DTERR_FIELD_OVERFLOW;
    /* be very sure we truncate towards zero (cf dtrunc()) */
    if (val >= 0)
        *ipart = (int) floor(val);
    else
        *ipart = (int) -floor(-val);
    *fpart = val - *ipart;
    return 0;
}

/*
 * Determine number of integral digits in a valid ISO 8601 number field
 * (we should ignore sign and any fraction part)
 */
static int
ISO8601IntegerWidth(char *fieldstart)
{
    /* We might have had a leading '-' */
    if (*fieldstart == '-')
        fieldstart++;
    return strspn(fieldstart, "0123456789");
}


/* DecodeISO8601Interval()
 *    Decode an ISO 8601 time interval of the "format with designators"
 *    (section 4.4.3.2) or "alternative format" (section 4.4.3.3)
 *    Examples:  P1D    for 1 day
 *               PT1H for 1 hour
 *               P2Y6M7DT1H30M for 2 years, 6 months, 7 days 1 hour 30 min
 *               P0002-06-07T01:30:00 the same value in alternative format
 *
 * Returns 0 if successful, DTERR code if bogus input detected.
 * Note: error code should be DTERR_BAD_FORMAT if input doesn't look like
 * ISO8601, otherwise this could cause unexpected error messages.
 * dtype, tm, fsec are output parameters.
 *
 *    A couple exceptions from the spec:
 *     - a week field ('W') may coexist with other units
 *     - allows decimals in fields other than the least significant unit.
 */
int
DecodeISO8601Interval(char *str,
                      int *dtype, struct pg_tm *tm, fsec_t *fsec)
{// #lizard forgives
    bool        datepart = true;
    bool        havefield = false;

    *dtype = DTK_DELTA;
    ClearPgTm(tm, fsec);

    if (strlen(str) < 2 || str[0] != 'P')
        return DTERR_BAD_FORMAT;

    str++;
    while (*str)
    {
        char       *fieldstart;
        int            val;
        double        fval;
        char        unit;
        int            dterr;

        if (*str == 'T')        /* T indicates the beginning of the time part */
        {
            datepart = false;
            havefield = false;
            str++;
            continue;
        }

        fieldstart = str;
        dterr = ParseISO8601Number(str, &str, &val, &fval);
        if (dterr)
            return dterr;

        /*
         * Note: we could step off the end of the string here.  Code below
         * *must* exit the loop if unit == '\0'.
         */
        unit = *str++;

        if (datepart)
        {
            switch (unit)        /* before T: Y M W D */
            {
                case 'Y':
                    tm->tm_year += val;
                    tm->tm_mon += (fval * MONTHS_PER_YEAR);
                    break;
                case 'M':
                    tm->tm_mon += val;
                    AdjustFractDays(fval, tm, fsec, DAYS_PER_MONTH);
                    break;
                case 'W':
                    tm->tm_mday += val * 7;
                    AdjustFractDays(fval, tm, fsec, 7);
                    break;
                case 'D':
                    tm->tm_mday += val;
                    AdjustFractSeconds(fval, tm, fsec, SECS_PER_DAY);
                    break;
                case 'T':        /* ISO 8601 4.4.3.3 Alternative Format / Basic */
                case '\0':
                    if (ISO8601IntegerWidth(fieldstart) == 8 && !havefield)
                    {
                        tm->tm_year += val / 10000;
                        tm->tm_mon += (val / 100) % 100;
                        tm->tm_mday += val % 100;
                        AdjustFractSeconds(fval, tm, fsec, SECS_PER_DAY);
                        if (unit == '\0')
                            return 0;
                        datepart = false;
                        havefield = false;
                        continue;
                    }
                    /* Else fall through to extended alternative format */
                case '-':        /* ISO 8601 4.4.3.3 Alternative Format,
                                 * Extended */
                    if (havefield)
                        return DTERR_BAD_FORMAT;

                    tm->tm_year += val;
                    tm->tm_mon += (fval * MONTHS_PER_YEAR);
                    if (unit == '\0')
                        return 0;
                    if (unit == 'T')
                    {
                        datepart = false;
                        havefield = false;
                        continue;
                    }

                    dterr = ParseISO8601Number(str, &str, &val, &fval);
                    if (dterr)
                        return dterr;
                    tm->tm_mon += val;
                    AdjustFractDays(fval, tm, fsec, DAYS_PER_MONTH);
                    if (*str == '\0')
                        return 0;
                    if (*str == 'T')
                    {
                        datepart = false;
                        havefield = false;
                        continue;
                    }
                    if (*str != '-')
                        return DTERR_BAD_FORMAT;
                    str++;

                    dterr = ParseISO8601Number(str, &str, &val, &fval);
                    if (dterr)
                        return dterr;
                    tm->tm_mday += val;
                    AdjustFractSeconds(fval, tm, fsec, SECS_PER_DAY);
                    if (*str == '\0')
                        return 0;
                    if (*str == 'T')
                    {
                        datepart = false;
                        havefield = false;
                        continue;
                    }
                    return DTERR_BAD_FORMAT;
                default:
                    /* not a valid date unit suffix */
                    return DTERR_BAD_FORMAT;
            }
        }
        else
        {
            switch (unit)        /* after T: H M S */
            {
                case 'H':
                    tm->tm_hour += val;
                    AdjustFractSeconds(fval, tm, fsec, SECS_PER_HOUR);
                    break;
                case 'M':
                    tm->tm_min += val;
                    AdjustFractSeconds(fval, tm, fsec, SECS_PER_MINUTE);
                    break;
                case 'S':
                    tm->tm_sec += val;
                    AdjustFractSeconds(fval, tm, fsec, 1);
                    break;
                case '\0':        /* ISO 8601 4.4.3.3 Alternative Format */
                    if (ISO8601IntegerWidth(fieldstart) == 6 && !havefield)
                    {
                        tm->tm_hour += val / 10000;
                        tm->tm_min += (val / 100) % 100;
                        tm->tm_sec += val % 100;
                        AdjustFractSeconds(fval, tm, fsec, 1);
                        return 0;
                    }
                    /* Else fall through to extended alternative format */
                case ':':        /* ISO 8601 4.4.3.3 Alternative Format,
                                 * Extended */
                    if (havefield)
                        return DTERR_BAD_FORMAT;

                    tm->tm_hour += val;
                    AdjustFractSeconds(fval, tm, fsec, SECS_PER_HOUR);
                    if (unit == '\0')
                        return 0;

                    dterr = ParseISO8601Number(str, &str, &val, &fval);
                    if (dterr)
                        return dterr;
                    tm->tm_min += val;
                    AdjustFractSeconds(fval, tm, fsec, SECS_PER_MINUTE);
                    if (*str == '\0')
                        return 0;
                    if (*str != ':')
                        return DTERR_BAD_FORMAT;
                    str++;

                    dterr = ParseISO8601Number(str, &str, &val, &fval);
                    if (dterr)
                        return dterr;
                    tm->tm_sec += val;
                    AdjustFractSeconds(fval, tm, fsec, 1);
                    if (*str == '\0')
                        return 0;
                    return DTERR_BAD_FORMAT;

                default:
                    /* not a valid time unit suffix */
                    return DTERR_BAD_FORMAT;
            }
        }

        havefield = true;
    }

    return 0;
}


/* DecodeUnits()
 * Decode text string using lookup table.
 *
 * This routine recognizes keywords associated with time interval units.
 *
 * Given string must be lowercased already.
 *
 * Implement a cache lookup since it is likely that dates
 *    will be related in format.
 */
int
DecodeUnits(int field, char *lowtoken, int *val)
{
    int            type;
    const datetkn *tp;

    tp = deltacache[field];
    /* use strncmp so that we match truncated tokens */
    if (tp == NULL || strncmp(lowtoken, tp->token, TOKMAXLEN) != 0)
    {
        tp = datebsearch(lowtoken, deltatktbl, szdeltatktbl);
    }
    if (tp == NULL)
    {
        type = UNKNOWN_FIELD;
        *val = 0;
    }
    else
    {
        deltacache[field] = tp;
        type = tp->type;
        *val = tp->value;
    }

    return type;
}                                /* DecodeUnits() */

/*
 * Report an error detected by one of the datetime input processing routines.
 *
 * dterr is the error code, str is the original input string, datatype is
 * the name of the datatype we were trying to accept.
 *
 * Note: it might seem useless to distinguish DTERR_INTERVAL_OVERFLOW and
 * DTERR_TZDISP_OVERFLOW from DTERR_FIELD_OVERFLOW, but SQL99 mandates three
 * separate SQLSTATE codes, so ...
 */
void
DateTimeParseError(int dterr, const char *str, const char *datatype)
{
    switch (dterr)
    {
        case DTERR_FIELD_OVERFLOW:
            ereport(ERROR,
                    (errcode(ERRCODE_DATETIME_FIELD_OVERFLOW),
                     errmsg("date/time field value out of range: \"%s\"",
                            str)));
            break;
        case DTERR_MD_FIELD_OVERFLOW:
            /* <nanny>same as above, but add hint about DateStyle</nanny> */
            ereport(ERROR,
                    (errcode(ERRCODE_DATETIME_FIELD_OVERFLOW),
                     errmsg("date/time field value out of range: \"%s\"",
                            str),
                     errhint("Perhaps you need a different \"datestyle\" setting.")));
            break;
        case DTERR_INTERVAL_OVERFLOW:
            ereport(ERROR,
                    (errcode(ERRCODE_INTERVAL_FIELD_OVERFLOW),
                     errmsg("interval field value out of range: \"%s\"",
                            str)));
            break;
        case DTERR_TZDISP_OVERFLOW:
            ereport(ERROR,
                    (errcode(ERRCODE_INVALID_TIME_ZONE_DISPLACEMENT_VALUE),
                     errmsg("time zone displacement out of range: \"%s\"",
                            str)));
            break;
        case DTERR_BAD_FORMAT:
        default:
            ereport(ERROR,
                    (errcode(ERRCODE_INVALID_DATETIME_FORMAT),
                     errmsg("invalid input syntax for type %s: \"%s\"",
                            datatype, str)));
            break;
    }
}

/* datebsearch()
 * Binary search -- from Knuth (6.2.1) Algorithm B.  Special case like this
 * is WAY faster than the generic bsearch().
 */
static const datetkn *
datebsearch(const char *key, const datetkn *base, int nel)
{
    if (nel > 0)
    {
        const datetkn *last = base + nel - 1,
                   *position;
        int            result;

        while (last >= base)
        {
            position = base + ((last - base) >> 1);
            /* precheck the first character for a bit of extra speed */
            result = (int) key[0] - (int) position->token[0];
            if (result == 0)
            {
                /* use strncmp so that we match truncated tokens */
                result = strncmp(key, position->token, TOKMAXLEN);
                if (result == 0)
                    return position;
            }
            if (result < 0)
                last = position - 1;
            else
                base = position + 1;
        }
    }
    return NULL;
}

/* EncodeTimezone()
 *        Copies representation of a numeric timezone offset to str.
 *
 * Returns a pointer to the new end of string.  No NUL terminator is put
 * there; callers are responsible for NUL terminating str themselves.
 */
static char *
EncodeTimezone(char *str, int tz, int style)
{
    int            hour,
                min,
                sec;

    sec = abs(tz);
    min = sec / SECS_PER_MINUTE;
    sec -= min * SECS_PER_MINUTE;
    hour = min / MINS_PER_HOUR;
    min -= hour * MINS_PER_HOUR;

    /* TZ is negated compared to sign we wish to display ... */
    *str++ = (tz <= 0 ? '+' : '-');

    if (sec != 0)
    {
        str = pg_ltostr_zeropad(str, hour, 2);
        *str++ = ':';
        str = pg_ltostr_zeropad(str, min, 2);
        *str++ = ':';
        str = pg_ltostr_zeropad(str, sec, 2);
    }
    else if (min != 0 || style == USE_XSD_DATES)
    {
        str = pg_ltostr_zeropad(str, hour, 2);
        *str++ = ':';
        str = pg_ltostr_zeropad(str, min, 2);
    }
    else
        str = pg_ltostr_zeropad(str, hour, 2);
    return str;
}

/* EncodeDateOnly()
 * Encode date as local time.
 */
void
EncodeDateOnly(struct pg_tm *tm, int style, char *str)
{// #lizard forgives
    Assert(tm->tm_mon >= 1 && tm->tm_mon <= MONTHS_PER_YEAR);

    switch (style)
    {
        case USE_ISO_DATES:
        case USE_XSD_DATES:
            /* compatible with ISO date formats */
            str = pg_ltostr_zeropad(str,
                                    (tm->tm_year > 0) ? tm->tm_year : -(tm->tm_year - 1), 4);
            *str++ = '-';
            str = pg_ltostr_zeropad(str, tm->tm_mon, 2);
            *str++ = '-';
            str = pg_ltostr_zeropad(str, tm->tm_mday, 2);
            break;

        case USE_SQL_DATES:
            /* compatible with Oracle/Ingres date formats */
            if (DateOrder == DATEORDER_DMY)
            {
                str = pg_ltostr_zeropad(str, tm->tm_mday, 2);
                *str++ = '/';
                str = pg_ltostr_zeropad(str, tm->tm_mon, 2);
            }
            else
            {
                str = pg_ltostr_zeropad(str, tm->tm_mon, 2);
                *str++ = '/';
                str = pg_ltostr_zeropad(str, tm->tm_mday, 2);
            }
            *str++ = '/';
            str = pg_ltostr_zeropad(str,
                                    (tm->tm_year > 0) ? tm->tm_year : -(tm->tm_year - 1), 4);
            break;

        case USE_GERMAN_DATES:
            /* German-style date format */
            str = pg_ltostr_zeropad(str, tm->tm_mday, 2);
            *str++ = '.';
            str = pg_ltostr_zeropad(str, tm->tm_mon, 2);
            *str++ = '.';
            str = pg_ltostr_zeropad(str,
                                    (tm->tm_year > 0) ? tm->tm_year : -(tm->tm_year - 1), 4);
            break;

        case USE_POSTGRES_DATES:
        default:
            /* traditional date-only style for Postgres */
            if (DateOrder == DATEORDER_DMY)
            {
                str = pg_ltostr_zeropad(str, tm->tm_mday, 2);
                *str++ = '-';
                str = pg_ltostr_zeropad(str, tm->tm_mon, 2);
            }
            else
            {
                str = pg_ltostr_zeropad(str, tm->tm_mon, 2);
                *str++ = '-';
                str = pg_ltostr_zeropad(str, tm->tm_mday, 2);
            }
            *str++ = '-';
            str = pg_ltostr_zeropad(str,
                                    (tm->tm_year > 0) ? tm->tm_year : -(tm->tm_year - 1), 4);
            break;
    }

    if (tm->tm_year <= 0)
    {
        memcpy(str, " BC", 3);    /* Don't copy NUL */
        str += 3;
    }
    *str = '\0';
}


/* EncodeTimeOnly()
 * Encode time fields only.
 *
 * tm and fsec are the value to encode, print_tz determines whether to include
 * a time zone (the difference between time and timetz types), tz is the
 * numeric time zone offset, style is the date style, str is where to write the
 * output.
 */
void
EncodeTimeOnly(struct pg_tm *tm, fsec_t fsec, bool print_tz, int tz, int style, char *str)
{
    str = pg_ltostr_zeropad(str, tm->tm_hour, 2);
    *str++ = ':';
    str = pg_ltostr_zeropad(str, tm->tm_min, 2);
    *str++ = ':';
    str = AppendSeconds(str, tm->tm_sec, fsec, MAX_TIME_PRECISION, true);
    if (print_tz)
        str = EncodeTimezone(str, tz, style);
    *str = '\0';
}


/* EncodeDateTime()
 * Encode date and time interpreted as local time.
 *
 * tm and fsec are the value to encode, print_tz determines whether to include
 * a time zone (the difference between timestamp and timestamptz types), tz is
 * the numeric time zone offset, tzn is the textual time zone, which if
 * specified will be used instead of tz by some styles, style is the date
 * style, str is where to write the output.
 *
 * Supported date styles:
 *    Postgres - day mon hh:mm:ss yyyy tz
 *    SQL - mm/dd/yyyy hh:mm:ss.ss tz
 *    ISO - yyyy-mm-dd hh:mm:ss+/-tz
 *    German - dd.mm.yyyy hh:mm:ss tz
 *    XSD - yyyy-mm-ddThh:mm:ss.ss+/-tz
 */
void
EncodeDateTime(struct pg_tm *tm, fsec_t fsec, bool print_tz, int tz, const char *tzn, int style, char *str)
{// #lizard forgives
    int            day;

    Assert(tm->tm_mon >= 1 && tm->tm_mon <= MONTHS_PER_YEAR);

    /*
     * Negative tm_isdst means we have no valid time zone translation.
     */
    if (tm->tm_isdst < 0)
        print_tz = false;

    switch (style)
    {
        case USE_ISO_DATES:
        case USE_XSD_DATES:
            /* Compatible with ISO-8601 date formats */
            str = pg_ltostr_zeropad(str,
                                    (tm->tm_year > 0) ? tm->tm_year : -(tm->tm_year - 1), 4);
            *str++ = '-';
            str = pg_ltostr_zeropad(str, tm->tm_mon, 2);
            *str++ = '-';
            str = pg_ltostr_zeropad(str, tm->tm_mday, 2);
            *str++ = (style == USE_ISO_DATES) ? ' ' : 'T';
            str = pg_ltostr_zeropad(str, tm->tm_hour, 2);
            *str++ = ':';
            str = pg_ltostr_zeropad(str, tm->tm_min, 2);
            *str++ = ':';
            str = AppendTimestampSeconds(str, tm, fsec);
            if (print_tz)
                str = EncodeTimezone(str, tz, style);
            break;

        case USE_SQL_DATES:
            /* Compatible with Oracle/Ingres date formats */
            if (DateOrder == DATEORDER_DMY)
            {
                str = pg_ltostr_zeropad(str, tm->tm_mday, 2);
                *str++ = '/';
                str = pg_ltostr_zeropad(str, tm->tm_mon, 2);
            }
            else
            {
                str = pg_ltostr_zeropad(str, tm->tm_mon, 2);
                *str++ = '/';
                str = pg_ltostr_zeropad(str, tm->tm_mday, 2);
            }
            *str++ = '/';
            str = pg_ltostr_zeropad(str,
                                    (tm->tm_year > 0) ? tm->tm_year : -(tm->tm_year - 1), 4);
            *str++ = ' ';
            str = pg_ltostr_zeropad(str, tm->tm_hour, 2);
            *str++ = ':';
            str = pg_ltostr_zeropad(str, tm->tm_min, 2);
            *str++ = ':';
            str = AppendTimestampSeconds(str, tm, fsec);

            /*
             * Note: the uses of %.*s in this function would be risky if the
             * timezone names ever contain non-ASCII characters.  However, all
             * TZ abbreviations in the IANA database are plain ASCII.
             */
            if (print_tz)
            {
                if (tzn)
                {
                    sprintf(str, " %.*s", MAXTZLEN, tzn);
                    str += strlen(str);
                }
                else
                    str = EncodeTimezone(str, tz, style);
            }
            break;

        case USE_GERMAN_DATES:
            /* German variant on European style */
            str = pg_ltostr_zeropad(str, tm->tm_mday, 2);
            *str++ = '.';
            str = pg_ltostr_zeropad(str, tm->tm_mon, 2);
            *str++ = '.';
            str = pg_ltostr_zeropad(str,
                                    (tm->tm_year > 0) ? tm->tm_year : -(tm->tm_year - 1), 4);
            *str++ = ' ';
            str = pg_ltostr_zeropad(str, tm->tm_hour, 2);
            *str++ = ':';
            str = pg_ltostr_zeropad(str, tm->tm_min, 2);
            *str++ = ':';
            str = AppendTimestampSeconds(str, tm, fsec);

            if (print_tz)
            {
                if (tzn)
                {
                    sprintf(str, " %.*s", MAXTZLEN, tzn);
                    str += strlen(str);
                }
                else
                    str = EncodeTimezone(str, tz, style);
            }
            break;

        case USE_POSTGRES_DATES:
        default:
            /* Backward-compatible with traditional Postgres abstime dates */
            day = date2j(tm->tm_year, tm->tm_mon, tm->tm_mday);
            tm->tm_wday = j2day(day);
            memcpy(str, days[tm->tm_wday], 3);
            str += 3;
            *str++ = ' ';
            if (DateOrder == DATEORDER_DMY)
            {
                str = pg_ltostr_zeropad(str, tm->tm_mday, 2);
                *str++ = ' ';
                memcpy(str, months[tm->tm_mon - 1], 3);
                str += 3;
            }
            else
            {
                memcpy(str, months[tm->tm_mon - 1], 3);
                str += 3;
                *str++ = ' ';
                str = pg_ltostr_zeropad(str, tm->tm_mday, 2);
            }
            *str++ = ' ';
            str = pg_ltostr_zeropad(str, tm->tm_hour, 2);
            *str++ = ':';
            str = pg_ltostr_zeropad(str, tm->tm_min, 2);
            *str++ = ':';
            str = AppendTimestampSeconds(str, tm, fsec);
            *str++ = ' ';
            str = pg_ltostr_zeropad(str,
                                    (tm->tm_year > 0) ? tm->tm_year : -(tm->tm_year - 1), 4);

            if (print_tz)
            {
                if (tzn)
                {
                    sprintf(str, " %.*s", MAXTZLEN, tzn);
                    str += strlen(str);
                }
                else
                {
                    /*
                     * We have a time zone, but no string version. Use the
                     * numeric form, but be sure to include a leading space to
                     * avoid formatting something which would be rejected by
                     * the date/time parser later. - thomas 2001-10-19
                     */
                    *str++ = ' ';
                    str = EncodeTimezone(str, tz, style);
                }
            }
            break;
    }

    if (tm->tm_year <= 0)
    {
        memcpy(str, " BC", 3);    /* Don't copy NUL */
        str += 3;
    }
    *str = '\0';
}


/*
 * Helper functions to avoid duplicated code in EncodeInterval.
 */

/* Append an ISO-8601-style interval field, but only if value isn't zero */
static char *
AddISO8601IntPart(char *cp, int value, char units)
{
    if (value == 0)
        return cp;
    sprintf(cp, "%d%c", value, units);
    return cp + strlen(cp);
}

/* Append a postgres-style interval field, but only if value isn't zero */
static char *
AddPostgresIntPart(char *cp, int value, const char *units,
                   bool *is_zero, bool *is_before)
{
    if (value == 0)
        return cp;
    sprintf(cp, "%s%s%d %s%s",
            (!*is_zero) ? " " : "",
            (*is_before && value > 0) ? "+" : "",
            value,
            units,
            (value != 1) ? "s" : "");

    /*
     * Each nonzero field sets is_before for (only) the next one.  This is a
     * tad bizarre but it's how it worked before...
     */
    *is_before = (value < 0);
    *is_zero = FALSE;
    return cp + strlen(cp);
}

/* Append a verbose-style interval field, but only if value isn't zero */
static char *
AddVerboseIntPart(char *cp, int value, const char *units,
                  bool *is_zero, bool *is_before)
{
    if (value == 0)
        return cp;
    /* first nonzero value sets is_before */
    if (*is_zero)
    {
        *is_before = (value < 0);
        value = abs(value);
    }
    else if (*is_before)
        value = -value;
    sprintf(cp, " %d %s%s", value, units, (value == 1) ? "" : "s");
    *is_zero = FALSE;
    return cp + strlen(cp);
}


/* EncodeInterval()
 * Interpret time structure as a delta time and convert to string.
 *
 * Support "traditional Postgres" and ISO-8601 styles.
 * Actually, afaik ISO does not address time interval formatting,
 *    but this looks similar to the spec for absolute date/time.
 * - thomas 1998-04-30
 *
 * Actually, afaik, ISO 8601 does specify formats for "time
 * intervals...[of the]...format with time-unit designators", which
 * are pretty ugly.  The format looks something like
 *       P1Y1M1DT1H1M1.12345S
 * but useful for exchanging data with computers instead of humans.
 * - ron 2003-07-14
 *
 * And ISO's SQL 2008 standard specifies standards for
 * "year-month literal"s (that look like '2-3') and
 * "day-time literal"s (that look like ('4 5:6:7')
 */
void
EncodeInterval(struct pg_tm *tm, fsec_t fsec, int style, char *str)
{// #lizard forgives
    char       *cp = str;
    int            year = tm->tm_year;
    int            mon = tm->tm_mon;
    int            mday = tm->tm_mday;
    int            hour = tm->tm_hour;
    int            min = tm->tm_min;
    int            sec = tm->tm_sec;
    bool        is_before = FALSE;
    bool        is_zero = TRUE;

#ifdef _PG_ORCL_
    if (enable_oracle_compatible)
    {
        if (sec >= SECS_PER_MINUTE || sec + SECS_PER_MINUTE <= 0)
        {
            min += (sec / SECS_PER_MINUTE);
            sec %= SECS_PER_MINUTE;
        }

        if (min >= MINS_PER_HOUR || min + MINS_PER_HOUR <= 0)
        {
            hour += (min / MINS_PER_HOUR);
            min %= MINS_PER_HOUR;
        }

        if (hour >= HOURS_PER_DAY || hour + HOURS_PER_DAY <= 0)
        {
            mday += (hour / HOURS_PER_DAY);
            hour %= HOURS_PER_DAY;
        }

        if (mon >= MONTHS_PER_YEAR || mon + MONTHS_PER_YEAR <= 0)
        {
            year += (mon / MONTHS_PER_YEAR);
            mon %= MONTHS_PER_YEAR;
        }
    }
#endif

    /*
     * The sign of year and month are guaranteed to match, since they are
     * stored internally as "month". But we'll need to check for is_before and
     * is_zero when determining the signs of day and hour/minute/seconds
     * fields.
     */
    switch (style)
    {
            /* SQL Standard interval format */
        case INTSTYLE_SQL_STANDARD:
            {
                bool        has_negative = year < 0 || mon < 0 ||
                mday < 0 || hour < 0 ||
                min < 0 || sec < 0 || fsec < 0;
                bool        has_positive = year > 0 || mon > 0 ||
                mday > 0 || hour > 0 ||
                min > 0 || sec > 0 || fsec > 0;
                bool        has_year_month = year != 0 || mon != 0;
                bool        has_day_time = mday != 0 || hour != 0 ||
                min != 0 || sec != 0 || fsec != 0;
                bool        has_day = mday != 0;
                bool        sql_standard_value = !(has_negative && has_positive) &&
                !(has_year_month && has_day_time);

                /*
                 * SQL Standard wants only 1 "<sign>" preceding the whole
                 * interval ... but can't do that if mixed signs.
                 */
                if (has_negative && sql_standard_value)
                {
                    *cp++ = '-';
                    year = -year;
                    mon = -mon;
                    mday = -mday;
                    hour = -hour;
                    min = -min;
                    sec = -sec;
                    fsec = -fsec;
                }

                if (!has_negative && !has_positive)
                {
                    sprintf(cp, "0");
                }
                else if (!sql_standard_value)
                {
                    /*
                     * For non sql-standard interval values, force outputting
                     * the signs to avoid ambiguities with intervals with
                     * mixed sign components.
                     */
                    char        year_sign = (year < 0 || mon < 0) ? '-' : '+';
                    char        day_sign = (mday < 0) ? '-' : '+';
                    char        sec_sign = (hour < 0 || min < 0 ||
                                            sec < 0 || fsec < 0) ? '-' : '+';

                    sprintf(cp, "%c%d-%d %c%d %c%d:%02d:",
                            year_sign, abs(year), abs(mon),
                            day_sign, abs(mday),
                            sec_sign, abs(hour), abs(min));
                    cp += strlen(cp);
                    cp = AppendSeconds(cp, sec, fsec, MAX_INTERVAL_PRECISION, true);
                    *cp = '\0';
                }
                else if (has_year_month)
                {
                    sprintf(cp, "%d-%d", year, mon);
                }
                else if (has_day)
                {
                    sprintf(cp, "%d %d:%02d:", mday, hour, min);
                    cp += strlen(cp);
                    cp = AppendSeconds(cp, sec, fsec, MAX_INTERVAL_PRECISION, true);
                    *cp = '\0';
                }
                else
                {
                    sprintf(cp, "%d:%02d:", hour, min);
                    cp += strlen(cp);
                    cp = AppendSeconds(cp, sec, fsec, MAX_INTERVAL_PRECISION, true);
                    *cp = '\0';
                }
            }
            break;

            /* ISO 8601 "time-intervals by duration only" */
        case INTSTYLE_ISO_8601:
            /* special-case zero to avoid printing nothing */
            if (year == 0 && mon == 0 && mday == 0 &&
                hour == 0 && min == 0 && sec == 0 && fsec == 0)
            {
                sprintf(cp, "PT0S");
                break;
            }
            *cp++ = 'P';
            cp = AddISO8601IntPart(cp, year, 'Y');
            cp = AddISO8601IntPart(cp, mon, 'M');
            cp = AddISO8601IntPart(cp, mday, 'D');
            if (hour != 0 || min != 0 || sec != 0 || fsec != 0)
                *cp++ = 'T';
            cp = AddISO8601IntPart(cp, hour, 'H');
            cp = AddISO8601IntPart(cp, min, 'M');
            if (sec != 0 || fsec != 0)
            {
                if (sec < 0 || fsec < 0)
                    *cp++ = '-';
                cp = AppendSeconds(cp, sec, fsec, MAX_INTERVAL_PRECISION, false);
                *cp++ = 'S';
                *cp++ = '\0';
            }
            break;

            /* Compatible with postgresql < 8.4 when DateStyle = 'iso' */
        case INTSTYLE_POSTGRES:
            cp = AddPostgresIntPart(cp, year, "year", &is_zero, &is_before);

            /*
             * Ideally we should spell out "month" like we do for "year" and
             * "day".  However, for backward compatibility, we can't easily
             * fix this.  bjm 2011-05-24
             */
            cp = AddPostgresIntPart(cp, mon, "mon", &is_zero, &is_before);
            cp = AddPostgresIntPart(cp, mday, "day", &is_zero, &is_before);
            if (is_zero || hour != 0 || min != 0 || sec != 0 || fsec != 0)
            {
                bool        minus = (hour < 0 || min < 0 || sec < 0 || fsec < 0);

                sprintf(cp, "%s%s%02d:%02d:",
                        is_zero ? "" : " ",
                        (minus ? "-" : (is_before ? "+" : "")),
                        abs(hour), abs(min));
                cp += strlen(cp);
                cp = AppendSeconds(cp, sec, fsec, MAX_INTERVAL_PRECISION, true);
                *cp = '\0';
            }
            break;

            /* Compatible with postgresql < 8.4 when DateStyle != 'iso' */
        case INTSTYLE_POSTGRES_VERBOSE:
        default:
            strcpy(cp, "@");
            cp++;
            cp = AddVerboseIntPart(cp, year, "year", &is_zero, &is_before);
            cp = AddVerboseIntPart(cp, mon, "mon", &is_zero, &is_before);
            cp = AddVerboseIntPart(cp, mday, "day", &is_zero, &is_before);
            cp = AddVerboseIntPart(cp, hour, "hour", &is_zero, &is_before);
            cp = AddVerboseIntPart(cp, min, "min", &is_zero, &is_before);
            if (sec != 0 || fsec != 0)
            {
                *cp++ = ' ';
                if (sec < 0 || (sec == 0 && fsec < 0))
                {
                    if (is_zero)
                        is_before = TRUE;
                    else if (!is_before)
                        *cp++ = '-';
                }
                else if (is_before)
                    *cp++ = '-';
                cp = AppendSeconds(cp, sec, fsec, MAX_INTERVAL_PRECISION, false);
                sprintf(cp, " sec%s",
                        (abs(sec) != 1 || fsec != 0) ? "s" : "");
                is_zero = FALSE;
            }
            /* identically zero? then put in a unitless zero... */
            if (is_zero)
                strcat(cp, " 0");
            if (is_before)
                strcat(cp, " ago");
            break;
    }
}


/*
 * We've been burnt by stupid errors in the ordering of the datetkn tables
 * once too often.  Arrange to check them during postmaster start.
 */
static bool
CheckDateTokenTable(const char *tablename, const datetkn *base, int nel)
{
    bool        ok = true;
    int            i;

    for (i = 0; i < nel; i++)
    {
        /* check for token strings that don't fit */
        if (strlen(base[i].token) > TOKMAXLEN)
        {
            /* %.*s is safe since all our tokens are ASCII */
            elog(LOG, "token too long in %s table: \"%.*s\"",
                 tablename,
                 TOKMAXLEN + 1, base[i].token);
            ok = false;
            break;                /* don't risk applying strcmp */
        }
        /* check for out of order */
        if (i > 0 &&
            strcmp(base[i - 1].token, base[i].token) >= 0)
        {
            elog(LOG, "ordering error in %s table: \"%s\" >= \"%s\"",
                 tablename,
                 base[i - 1].token,
                 base[i].token);
            ok = false;
        }
    }
    return ok;
}

bool
CheckDateTokenTables(void)
{
    bool        ok = true;

    Assert(UNIX_EPOCH_JDATE == date2j(1970, 1, 1));
    Assert(POSTGRES_EPOCH_JDATE == date2j(2000, 1, 1));

    ok &= CheckDateTokenTable("datetktbl", datetktbl, szdatetktbl);
    ok &= CheckDateTokenTable("deltatktbl", deltatktbl, szdeltatktbl);
    return ok;
}

/*
 * Common code for temporal protransform functions.  Types time, timetz,
 * timestamp and timestamptz each have a range of allowed precisions.  An
 * unspecified precision is rigorously equivalent to the highest specifiable
 * precision.
 *
 * Note: timestamp_scale throws an error when the typmod is out of range, but
 * we can't get there from a cast: our typmodin will have caught it already.
 */
Node *
TemporalTransform(int32 max_precis, Node *node)
{
    FuncExpr   *expr = castNode(FuncExpr, node);
    Node       *ret = NULL;
    Node       *typmod;

    Assert(list_length(expr->args) >= 2);

    typmod = (Node *) lsecond(expr->args);

    if (IsA(typmod, Const) &&!((Const *) typmod)->constisnull)
    {
        Node       *source = (Node *) linitial(expr->args);
        int32        old_precis = exprTypmod(source);
        int32        new_precis = DatumGetInt32(((Const *) typmod)->constvalue);

        if (new_precis < 0 || new_precis == max_precis ||
            (old_precis >= 0 && new_precis >= old_precis))
            ret = relabel_to_typmod(source, new_precis);
    }

    return ret;
}

/*
 * This function gets called during timezone config file load or reload
 * to create the final array of timezone tokens.  The argument array
 * is already sorted in name order.
 *
 * The result is a TimeZoneAbbrevTable (which must be a single malloc'd chunk)
 * or NULL on malloc failure.  No other error conditions are defined.
 */
TimeZoneAbbrevTable *
ConvertTimeZoneAbbrevs(struct tzEntry *abbrevs, int n)
{
    TimeZoneAbbrevTable *tbl;
    Size        tbl_size;
    int            i;

    /* Space for fixed fields and datetkn array */
    tbl_size = offsetof(TimeZoneAbbrevTable, abbrevs) +
        n * sizeof(datetkn);
    tbl_size = MAXALIGN(tbl_size);
    /* Count up space for dynamic abbreviations */
    for (i = 0; i < n; i++)
    {
        struct tzEntry *abbr = abbrevs + i;

        if (abbr->zone != NULL)
        {
            Size        dsize;

            dsize = offsetof(DynamicZoneAbbrev, zone) +
                strlen(abbr->zone) + 1;
            tbl_size += MAXALIGN(dsize);
        }
    }

    /* Alloc the result ... */
    tbl = malloc(tbl_size);
    if (!tbl)
        return NULL;

    /* ... and fill it in */
    tbl->tblsize = tbl_size;
    tbl->numabbrevs = n;
    /* in this loop, tbl_size reprises the space calculation above */
    tbl_size = offsetof(TimeZoneAbbrevTable, abbrevs) +
        n * sizeof(datetkn);
    tbl_size = MAXALIGN(tbl_size);
    for (i = 0; i < n; i++)
    {
        struct tzEntry *abbr = abbrevs + i;
        datetkn    *dtoken = tbl->abbrevs + i;

        /* use strlcpy to truncate name if necessary */
        strlcpy(dtoken->token, abbr->abbrev, TOKMAXLEN + 1);
        if (abbr->zone != NULL)
        {
            /* Allocate a DynamicZoneAbbrev for this abbreviation */
            DynamicZoneAbbrev *dtza;
            Size        dsize;

            dtza = (DynamicZoneAbbrev *) ((char *) tbl + tbl_size);
            dtza->tz = NULL;
            strcpy(dtza->zone, abbr->zone);

            dtoken->type = DYNTZ;
            /* value is offset from table start to DynamicZoneAbbrev */
            dtoken->value = (int32) tbl_size;

            dsize = offsetof(DynamicZoneAbbrev, zone) +
                strlen(abbr->zone) + 1;
            tbl_size += MAXALIGN(dsize);
        }
        else
        {
            dtoken->type = abbr->is_dst ? DTZ : TZ;
            dtoken->value = abbr->offset;
        }
    }

    /* Assert the two loops above agreed on size calculations */
    Assert(tbl->tblsize == tbl_size);

    /* Check the ordering, if testing */
    Assert(CheckDateTokenTable("timezone abbreviations", tbl->abbrevs, n));

    return tbl;
}

/*
 * Install a TimeZoneAbbrevTable as the active table.
 *
 * Caller is responsible that the passed table doesn't go away while in use.
 */
void
InstallTimeZoneAbbrevs(TimeZoneAbbrevTable *tbl)
{
    zoneabbrevtbl = tbl;
    /* reset abbrevcache, which may contain pointers into old table */
    memset(abbrevcache, 0, sizeof(abbrevcache));
}

/*
 * Helper subroutine to locate pg_tz timezone for a dynamic abbreviation.
 */
static pg_tz *
FetchDynamicTimeZone(TimeZoneAbbrevTable *tbl, const datetkn *tp)
{
    DynamicZoneAbbrev *dtza;

    /* Just some sanity checks to prevent indexing off into nowhere */
    Assert(tp->type == DYNTZ);
    Assert(tp->value > 0 && tp->value < tbl->tblsize);

    dtza = (DynamicZoneAbbrev *) ((char *) tbl + tp->value);

    /* Look up the underlying zone if we haven't already */
    if (dtza->tz == NULL)
    {
        dtza->tz = pg_tzset(dtza->zone);

        /*
         * Ideally we'd let the caller ereport instead of doing it here, but
         * then there is no way to report the bad time zone name.
         */
        if (dtza->tz == NULL)
            ereport(ERROR,
                    (errcode(ERRCODE_CONFIG_FILE_ERROR),
                     errmsg("time zone \"%s\" not recognized",
                            dtza->zone),
                     errdetail("This time zone name appears in the configuration file for time zone abbreviation \"%s\".",
                               tp->token)));
    }
    return dtza->tz;
}


/*
 * This set-returning function reads all the available time zone abbreviations
 * and returns a set of (abbrev, utc_offset, is_dst).
 */
Datum
pg_timezone_abbrevs(PG_FUNCTION_ARGS)
{// #lizard forgives
    FuncCallContext *funcctx;
    int           *pindex;
    Datum        result;
    HeapTuple    tuple;
    Datum        values[3];
    bool        nulls[3];
    const datetkn *tp;
    char        buffer[TOKMAXLEN + 1];
    int            gmtoffset;
    bool        is_dst;
    unsigned char *p;
    struct pg_tm tm;
    Interval   *resInterval;

    /* stuff done only on the first call of the function */
    if (SRF_IS_FIRSTCALL())
    {
        TupleDesc    tupdesc;
        MemoryContext oldcontext;

        /* create a function context for cross-call persistence */
        funcctx = SRF_FIRSTCALL_INIT();

        /*
         * switch to memory context appropriate for multiple function calls
         */
        oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);

        /* allocate memory for user context */
        pindex = (int *) palloc(sizeof(int));
        *pindex = 0;
        funcctx->user_fctx = (void *) pindex;

        /*
         * build tupdesc for result tuples. This must match this function's
         * pg_proc entry!
         */
        tupdesc = CreateTemplateTupleDesc(3, false);
        TupleDescInitEntry(tupdesc, (AttrNumber) 1, "abbrev",
                           TEXTOID, -1, 0);
        TupleDescInitEntry(tupdesc, (AttrNumber) 2, "utc_offset",
                           INTERVALOID, -1, 0);
        TupleDescInitEntry(tupdesc, (AttrNumber) 3, "is_dst",
                           BOOLOID, -1, 0);

        funcctx->tuple_desc = BlessTupleDesc(tupdesc);
        MemoryContextSwitchTo(oldcontext);
    }

    /* stuff done on every call of the function */
    funcctx = SRF_PERCALL_SETUP();
    pindex = (int *) funcctx->user_fctx;

    if (zoneabbrevtbl == NULL ||
        *pindex >= zoneabbrevtbl->numabbrevs)
        SRF_RETURN_DONE(funcctx);

    tp = zoneabbrevtbl->abbrevs + *pindex;

    switch (tp->type)
    {
        case TZ:
            gmtoffset = tp->value;
            is_dst = false;
            break;
        case DTZ:
            gmtoffset = tp->value;
            is_dst = true;
            break;
        case DYNTZ:
            {
                /* Determine the current meaning of the abbrev */
                pg_tz       *tzp;
                TimestampTz now;
                int            isdst;

                tzp = FetchDynamicTimeZone(zoneabbrevtbl, tp);
                now = GetCurrentTransactionStartTimestamp();
                gmtoffset = -DetermineTimeZoneAbbrevOffsetTS(now,
                                                             tp->token,
                                                             tzp,
                                                             &isdst);
                is_dst = (bool) isdst;
                break;
            }
        default:
            elog(ERROR, "unrecognized timezone type %d", (int) tp->type);
            gmtoffset = 0;        /* keep compiler quiet */
            is_dst = false;
            break;
    }

    MemSet(nulls, 0, sizeof(nulls));

    /*
     * Convert name to text, using upcasing conversion that is the inverse of
     * what ParseDateTime() uses.
     */
    strlcpy(buffer, tp->token, sizeof(buffer));
    for (p = (unsigned char *) buffer; *p; p++)
        *p = pg_toupper(*p);

    values[0] = CStringGetTextDatum(buffer);

    /* Convert offset (in seconds) to an interval */
    MemSet(&tm, 0, sizeof(struct pg_tm));
    tm.tm_sec = gmtoffset;
    resInterval = (Interval *) palloc(sizeof(Interval));
    tm2interval(&tm, 0, resInterval);
    values[1] = IntervalPGetDatum(resInterval);

    values[2] = BoolGetDatum(is_dst);

    (*pindex)++;

    tuple = heap_form_tuple(funcctx->tuple_desc, values, nulls);
    result = HeapTupleGetDatum(tuple);

    SRF_RETURN_NEXT(funcctx, result);
}

/*
 * This set-returning function reads all the available full time zones
 * and returns a set of (name, abbrev, utc_offset, is_dst).
 */
Datum
pg_timezone_names(PG_FUNCTION_ARGS)
{// #lizard forgives
    MemoryContext oldcontext;
    FuncCallContext *funcctx;
    pg_tzenum  *tzenum;
    pg_tz       *tz;
    Datum        result;
    HeapTuple    tuple;
    Datum        values[4];
    bool        nulls[4];
    int            tzoff;
    struct pg_tm tm;
    fsec_t        fsec;
    const char *tzn;
    Interval   *resInterval;
    struct pg_tm itm;

    /* stuff done only on the first call of the function */
    if (SRF_IS_FIRSTCALL())
    {
        TupleDesc    tupdesc;

        /* create a function context for cross-call persistence */
        funcctx = SRF_FIRSTCALL_INIT();

        /*
         * switch to memory context appropriate for multiple function calls
         */
        oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);

        /* initialize timezone scanning code */
        tzenum = pg_tzenumerate_start();
        funcctx->user_fctx = (void *) tzenum;

        /*
         * build tupdesc for result tuples. This must match this function's
         * pg_proc entry!
         */
        tupdesc = CreateTemplateTupleDesc(4, false);
        TupleDescInitEntry(tupdesc, (AttrNumber) 1, "name",
                           TEXTOID, -1, 0);
        TupleDescInitEntry(tupdesc, (AttrNumber) 2, "abbrev",
                           TEXTOID, -1, 0);
        TupleDescInitEntry(tupdesc, (AttrNumber) 3, "utc_offset",
                           INTERVALOID, -1, 0);
        TupleDescInitEntry(tupdesc, (AttrNumber) 4, "is_dst",
                           BOOLOID, -1, 0);

        funcctx->tuple_desc = BlessTupleDesc(tupdesc);
        MemoryContextSwitchTo(oldcontext);
    }

    /* stuff done on every call of the function */
    funcctx = SRF_PERCALL_SETUP();
    tzenum = (pg_tzenum *) funcctx->user_fctx;

    /* search for another zone to display */
    for (;;)
    {
        oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);
        tz = pg_tzenumerate_next(tzenum);
        MemoryContextSwitchTo(oldcontext);

        if (!tz)
        {
            pg_tzenumerate_end(tzenum);
            funcctx->user_fctx = NULL;
            SRF_RETURN_DONE(funcctx);
        }

        /* Convert now() to local time in this zone */
        if (timestamp2tm(GetCurrentTransactionStartTimestamp(),
                         &tzoff, &tm, &fsec, &tzn, tz) != 0)
            continue;            /* ignore if conversion fails */

        /*
         * Ignore zic's rather silly "Factory" time zone.  The long string
         * about "see zic manual page" is used in tzdata versions before
         * 2016g; we can drop it someday when we're pretty sure no such data
         * exists in the wild on platforms using --with-system-tzdata.  In
         * 2016g and later, the time zone abbreviation "-00" is used for
         * "Factory" as well as some invalid cases, all of which we can
         * reasonably omit from the pg_timezone_names view.
         */
        if (tzn && (strcmp(tzn, "-00") == 0 ||
                    strcmp(tzn, "Local time zone must be set--see zic manual page") == 0))
            continue;

        /* Found a displayable zone */
        break;
    }

    MemSet(nulls, 0, sizeof(nulls));

    values[0] = CStringGetTextDatum(pg_get_timezone_name(tz));
    values[1] = CStringGetTextDatum(tzn ? tzn : "");

    MemSet(&itm, 0, sizeof(struct pg_tm));
    itm.tm_sec = -tzoff;
    resInterval = (Interval *) palloc(sizeof(Interval));
    tm2interval(&itm, 0, resInterval);
    values[2] = IntervalPGetDatum(resInterval);

    values[3] = BoolGetDatum(tm.tm_isdst > 0);

    tuple = heap_form_tuple(funcctx->tuple_desc, values, nulls);
    result = HeapTupleGetDatum(tuple);

    SRF_RETURN_NEXT(funcctx, result);
}
